I'm actually wondering why a capsule is required at the lowest stage - Goddard did liquid fuel at a very small scale, sounding rockets, V-2, Sputnik - it was quite a while before more than dogs and chimps went into space. A really dumbed-down probe level (no reaction wheels and so-on) at a very small scale might be what you've got at low level, but allows you to do robotic missions early rather than after risking a bunch of your pilots. Then again, I'm a Noob who still hasn't landed on a planet other than Kerbal or orbited another planet other than in the tutorial. I'm not a power user.