Non-spacefaring societies are limited in influence and participation in interstellar society.
History & Background (Dossier)
Spacefaring societies gain tremendous advantages over societies unable to leave their own gravity well. Zero-G manufacturing, spacebourne telescopes, and much more are beyond the reach of non-spacefaring societies.
After the first visit by interstellar merchants, such societies become aware of their technological backwardness, often having negative psychological effects. Such experiences tend to accelerate the desire to purchase FTL technology or reverse-engineer it.