>>9967173The do a draft roughly every other year to shuffle people around, the logistical reason is basically WWE runs 3 tours Raw, SmackDown and their developmental program NXT, who tours mostly Florida. When Raw is on tv, Smackdown guys are wrestling in another city and vice versa, this weekend the Raw guys are in England while SD is here in the states.
on TV you don't notice it as much as people will crossover every week but if you go to a SD Tour you'll only see SD guys.
to freshen up match parings they do a draft, shuffle up the rosters and call up trainees from NXT.
They just make a big TV show out of it, and the two brands Raw and SD are in a quasi feud with each other and have matches against each other a few times a year.