It got me to thinking though. All the products so far have been set in the Realms, as are the Adventurer's League items. If all the adventures are set in the Realms, is it surprising that the majority of folks are playing in the Realms?
It's definitely a two-way effect.
I can speak for myself, that I started DMing with 3e, and it had Greyhawk as default setting. Even tho it only meant to have Greyhawk's deities in the PHB and basically nothing else about such setting in the core, because this was the only option to start with, I was essentially saying that our games were set in Greyhawk...
Except that there wasn't really anything more than this, and while searching websites for maps and adventure ideas, I eventually stumbled upon FR maps, so we were kind of playing in a Faerun world but with Greyhawk religions :/ (Incidentally, the first main 'named' location I picked from those maps was Neverwinter, without
any idea that it was so popular)
After a while, I found out that while there was basically no 3e support for Greyhawk, the FRCS was a highly popular and esteemed book, and that's why we switched over. But many Greyhawk deities also carried over so as not to invalidate previous adventures and PCs... soon it was a mess of a homebrew really

Not to mention the Planescape stuff that other DMs with experience dating back to AD&D brought to the table.
So yes I can say that now after 15 years I know which settings I like, but clearly the available support played a big role in determining which ones to play in the first place.