https://en.wikipedia.org/wiki/Orbital_inclination

In order to cover those northern/southern extremes, more expensive high inclination orbits are required (in the US these are launched from California). They are more expensive because you’re no longer getting the rotational velocity of the earth for free in your orbital velocity.

So for a LEO constellation you want to minimize the launches to high inclinations and keep the bulk in those juicy easterly ones.