The Williams Institute looked at the difference in the Top 10 most LGBT metropolitan areas from 1990 to 2014:
The substantial change in the position of Salt Lake City in the 1990 same-sex couple rankings compared to its position in the recent rankings based on LGBT identity offers evidence of increased LGBT visibility even in conservative states like Utah. This may be a factor in why, in 2015, Utah became the first state in the last seven years to pass a law that prohibits discrimination in the workplace and in public accommodation based on sexual orientation and gender identity. The majority of states still do not have such laws on their books. Substantial increases in LGBT visibility in more socially conservative places like Salt Lake City, Louisville, and Norfolk likely mean that these areas are not as different from cities like San Francisco, Austin, and Seattle (all with long histories of fostering social climates where LGBT people felt more comfortable) in their acceptance of the LGBT community today than they were twenty years ago.Basically, the entire country is more accepting as a whole so the geographical variation is much smaller (the difference between the #1 area of San Francisco at 6.2% and the median nationwide percentage of 3.6% is not that great) so that even the the area with the lowest LGBT population (unsurprisingly, Birmingham, Alabama) is only one percentage point below this mark.