Personally I like splitting up on streamlined things like ITF’s because it allows me to stretch my legs and flex my powers a little more. If I stick with the group on the first mission of a speed ITF, I use a few powers before everything is dead. If I run straight to the far back room, I get to really play a good bit. IOW: I run ahead to get an extra slice of the action.
Also a lot of people I play with are clearly more motivated by merits etc. than xp, so +1 to that being immaterial to a lot of people.