Reasons to build stuff in survival
Besides playing in a PVP server or doing the scenarios (which I don't really count as survival) there's no real reason to build stuff. Many videos say that the game is fueled by creativity and exploration, and while I love the concept I find there's not much reason to explore behind finding new mineral sources to build stuff. Also, some blocks have almost no use (In particular the oxygen farm, which in Earth-like planets is unneeded, and in space/moons it's borderline useless cause it's easier to find ice to feed into an Oxygen generator)
The problem of "why do things" was very lightly solved with the addition of NPC stations, where they asked you to get X of whatever material o go somewhere and escort a ship. This is an excellent beginning but turns repetitive soon, especially with little to no intervention from NPCs in most of these missions (except by the escort one). So here are some ideas that I think should be relatively easy to implement:
Food: Or rather nutrients. Its need would enhance the survival side of things (just don't exaggerate it xD) While I'd love it that you could actually plant stuff, and then have to harvest it (which, if intending to sell the produce in quantities would require the player to build a harvester :D) a much faster solution (and non-excluding of the harvesting idea) would be to make the oxygen farm also small several fruits and vegetables, which could then be tossed into an assembler (and the cooking decoration ;D) and produce nutrients, which could function just as an O2 bottle from the backpack of the engineer. Also, if/when NPC are available (crewman or maybe "villagers"?), you would need excess nutrients to feed your people. Also, this could/should be an expensive commodity when sold in outer space stations or stuff like that.
"Large Quests": The fact that ground and space NPC stations can appear, and those missions where you have to escort a ship from A to B and protect it from pirates should make this idea viable and (i hope) rather easy to implement. Just as those missions I just mentioned, you could occasionally find a mission from an archeology faction who will tell you that they've just uncovered the location of an ancient relic left by an ancient civilization (or an important device on an old abandoned outpost). They want this relic/device back, so you are contracted to get it, as they fear that if they wait till they can make it to the spot, the relic might have been stolen or otherwise lost. So they'll give you coordinates to where this site is, much like the actual missions. Thing is, they'll tell you that they need you to be as less invasive of the site as possible because they want to study it, hence, you'll receive a base reward for the artifact and a huge starting bonus, which will decrease the more you damage/grind the site, forcing you to actually think and build a proper device to extract the relic, instead of just grinding/drilling your way towards it.
A variation of the same thing could be a military contractor that tells you that a pirate group has stolen an encrypted drive or warheads or something like this (maybe even a hostage engineer in cryostasis??). No units are available so they are paying for mercenary work, that means you. Again, they'll feed you the coordinates, in which you would find bases of varying sizes, guarded with turrets and drones of several sizes (and maybe NPCs? :D) So you'll have to build some sort of assault contraption to deal with the defenders and then another contraption (or maybe the same?) to retrieve the thing and give it back to the contractor.
Other examples could be made, but these missions should be at least on another planet or asteroid pack, or at the very least, on the other side of the planet. Or at least more than 10km away.
"Small Quests": Remember when I talked about villagers? let's suppose you can build "housing" and then rent this rooms/apartments to NPCs. These NPCs could sometimes post short quests for you. For example: "Dave" tells you that his friend George was coming to see him, but he hasn't arrived nor communicated, and he has estimated coordinates of where he was when he last contacted you. You then go to those coordinates and find out that George's rover has crashed, and he needs picking up. So you pick him up and drive him back to Dave, where he will reward you with SC and maybe some random material. (I admit I'm taking this idea directly from starbound).
In a variation of the later, Dave could tell you that a delivery drone was bringing something and it crashed, or was attacked, and you need to retrieve the cargo. In a further variation, maybe the cargo was stolen and you have to track it down (maybe the pirates left a notepad with a beacon to come back for the rest, and there you can get the coordinates of where they are taking the cargo).
But... what if you don't want to create a village or take orders/missions from no stinking NPC? Some of these stations / crashed vehicles / old sites could still spawn, even with no mission (few, to save resources, but configurable, so if you have a beefy machine, more of these "events" will load with no need of a mission bein given). This would encourage exploration since it could wield valuable already made materials, and as for the relics you could take them for yourself or actually then go to an NPC station and "sell it" there, we'll assume that the interested party is grateful and will pay for the cargo as well (or almost as well, but never more than) as if you had taken the quest from them.
Last but not least: While a lot of these ideas are (i think) implementable without adding new NPCs, it would be ideal to have some npcs roaming around, not necessarily all hostile. But add some planetside drones too.
Attached to all of these: You may spawn far away from any NPC station, so a comm satellite should always spawn "near" (read: 10 to 20 km away from the player), the idea behind these if that when the player gets an antenna inside that range, he would pick up the location of these satellites and these would rely (or have it shown right away) the coordinate of the nearest NPC station. For added bonus a transmission could be heard (or read) telling you that nice job surviving and that at X coordinates there are some missions to be done if the player needs the cash and/or materials)