We've seen Floyd use it to great success earlier in his career and even today, he utilized it exceptionally against Mosley/Maidana etc etc. Why do fighters nowadays not use it?
I'm glad you ONLY talk about Floyd, instead going on anti-Pacquiao campaigns like Constable or whoever does towards Floyd. You're much less offensive.
I'd assume it requires great skill and timing, not something you can do easily. I mean you can say the same about the shoulder roll, there's a reason why Floyd is the p4p #1 today, because he can do things most other can't.
Typically, rolling to the outside or inside (more dangerous, if done wrong) of the jab sets up better shots and keeps one in closer proximity to land power shots, often without an opponent seeing them coming. Pull counters tend to be easier to spot and easier to counter or avoid. I think Floyd might have some trouble with the pull counter against another elite fighter, but the slower guys he usually fights seem to eat them all night.
Because it's high risk, hard to put power into, and requires you to be much faster than your opponent.
Maybe if the OP actually watched other fighters he would realize that it IS used.. Rigo, Andrade, Broner.... Only a certain style of fighter can do it. https://www.youtube.com/watch?v=QCSHhmZkvlc Watch some other fighters sometime (go to 21 seconds in) EDIT: What I will say is that there are far fewer fighters with basic fundamentals than there used to be.
A better question would be where the hell is the jab! It feels like it's becoming a lost art. ( little exaggerated) BUT lately I feel like I see more pole arms and paws than an actual jab.
Its something that trainers would not really teach their boxers unless you have fast reflexes like floyd or roy jones. Unless you wanna get knocked out if you have an average chin, the pull counter is in reality a big no-no for old school trainers