I think it's pretty pointless to point out the point of Orbiter. The genre of simulations, and esp. realistic(*) simulations, attracts people of a certain mindset. That includes overall erudition, curiosity and desire to discover, also patience and being not afraind of a huge learning curve.
Yes, a newcomer will have to read 'Go Play In Space', study the basics of orbital mechanics before he can jump into the Deltaglider and blast off. Yes, one will have to read (and understand) lots of fine manuals. And a general interest in (i.e. basic knowledge of) astronomy helps a lot too.
People of those qualities and abilities are generally able to understand the points of a space simulation without any additional guidelines, it's kind of obvious to them. Those who neither have the desire to learn nor the abilities, do not become orbinauts, I think it's that simple.
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* - meaning "plausible and sufficiently detailed". Falcon, Lockon, MSFS, Xplane are, but, say, Mechwarrior isn't.