Plain and simple, Friends is the single best television show of this generation. It's time for the world to accept that as fact. That's slightly besides the point here, but definitely worth mentioning.
One thing that most TV watchers can agree on, however, is that fans of the show have a somewhat freakish obsession with the Central Perk gang. It's not abnormal to encounter seemingly normal humans who actually have every single line of every single episode memorized. So, any slight change or edit to a scene of the show would certainly ruffle some feathers. Such is the case with this latest Friends viral vid—the Internet thought it would be funny to remix the show's opening credits and actually delete the music.
In other words, no "I'll Be There For You" equals just a lot of awkwardly quiet dancing. Major apologies to The Rembrandts. Also major apologies to the cast, because it's now clear how painful it must have been to shoot this bit.