Why does everyone use PF as a representation of the game?

[SeiyaSoiya]

Because PF is where the vast majority of players experience end-game content. If you polled the entire playerbase, I think the gap between players who solely use PF versus those who raid in statics would be much larger than we'd think.

and your source being?
every source I search for claims that the vast, vast majority of raiders are casual raiders who only raid 3h a week in a static made of 7 other friends
pf is only for the irrelevant minority of players who play more than 10h a day