What on Kerbin does Rep even do?

[makinyashikino]

What purpose does reputation even have? It seems pretty hard to get 0 rep, unless you crash your 50-Hitchhiker rocket. What happens when you reach 0 rep anyway?

[Godot]

AFAIK Reputation affects the number of contracts offered to you and how good they are ... guess, with Rep = 0 you´ll only get offered 1 star contracts that, only rarely, give you a good pay ... and only few companies will think you trustworthy enough in order to assist them with their endeavors

[tjsnh]

IIRC, the Devs posted that at the moment it just effects contracts (as Godot said) but in the future it will influence the quality of Kerbals applying to join your space program as well (and if any are willing to sign up at all!)

[Geschosskopf]

Also, in the future you will be able to convert Rep into Science and/or cash as needed. But for now, Rep just means more rewarding contracts.