It's true they can also take air from the surface. That's what makes them potential tankmates for bettas with no aeration in their tank.
Personally, I think they just make it an excuse to dash around the tank disrupting schools of fish. LOL
Cory1: "Hey, bubba, hold my beer and watch this."
Cory2: "Whatcha gonna do, Cletis?"
Cory1: "I'm gonna go 'get air' right through that school of tiger barbs over yonder. Watch them scatter, it's hilarious."
Cory2: "Ok, hang on. Let me get my vido camera."
.....they're a bunch of thrillseekers and adrenaline junkies, if you ask me. :D