the majority of Americans live in coastal states.
the majority of Americans live ins suburban/urban,
LBGTQ just follow this trend a bit more, because LBGTQs are probably more likely to seek city life to be near a higher population of queers than two or three that live in a rural town of 1000.
What I do notice is a there are higher densities of Gays in resort areas and "nicer" areas. Not sure why, but there you have it.