Mostly they have to pick their launch site so the flight path, headed into the right orbital plane, doesn't pass over populated areas. It would be rude to drop boosters and stages on people. https://history.nasa.gov/EP-165/p25.htm
Interesting fact, Israel is one of the few countries on earth that regularly launches into retrogade LEO (first stage flight path over ocean), because of the extreme political considerations around lobbing something that looks like an ICBM over their eastern neighbours. And the problem with dropping spent first stages on everywhere east of them.
