If you have to ask you'll never understand...

All but the best DJs are busy for pretty much the entire time they're playing - maybe a 30 seconds break here or there, but the rest of the time is concentrating.
Super quick rundown from bedroom dj-ing:
find next record (needs to flow from current)
find correct track on record
find first beat new record, and 16th or 32nd beat of playing record
beatmatch (adjust speed of new record by ear)
adjust eq (every single song is adjusted bass/middle/treble for best sound)
find point in the record that you know will mix to point of outgoing record
Bring in new record in sync at the right point
adjust to keep in sync, eq, maybe do some tricks here or there
drop old record out (slow or fast)
remove old record, put in cover, box
breathe for 5 secs
repeat
Most of the record control is done by touch, and one bad touch on a 'live' record will stuff the whole thing up.
I agree about the egos... and the crowd. Can't stand either, generally.
I have to disagree about talent or musicianship, when I was young I used to play bass and I can assure you that the bass player of AC/DC, for example, has to hit about 10 notes in most tunes. You could do it brain dead and it's so much less work than what I've described above.
There is some physical and mental skill in it, and really good dj's know an incredible amount of music - really really well. That's what makes the best dj's - the tunes they pick, over the whole set.Like it or not record decks are instruments too, because they're live and if you touch them wrong the whole show comes to a screeching halt - literally sometimes.