A couple of things to consider:
A DJ playing in a live set most likely is spinning with a sound setup and equipment that he or she is not accustomed to. That could have some influence in the performance

Also, not all records are perfect. Some records may have a pitch fluctuation, and I'm still not sure if its caused by warpeness of a vinyl or the off center cut,,, maybe both. But I bet even pro djs deal with fucked records from time to time.

Finally, the crowd, the pressure, distractions. That can always influence one's technical skills. Well one other thing I forgot to mention, some djs bring out about 300 vinyls to a gig, and they decide to play what they feel best at the moment, so they may not remember every track, every beat or bar in a track... For the most part they may have the records down perfect, but they may forget the amount of bars on one melody or two.

As for anyone mixing in bedroom (like me)-- Yeah I've found to be really picky and nick at every little error a pro does on stage. But I realize that at home, there is no type of pressure. The environment remains the same and I'm using the same equipment that I practice on a daily basis. I am fully adjusted to my mini sound system, powered by the monitor speakers that I use.

I don't know if it's just me, but when I play somewhere else other than home, I feel a bit akward,,,, and I need to get a feel for the sound system and equipment. Oh, and when I say equipment, I'm talking about mixer and sound system, not really turntables, cause 1200s are most likely used at the big events that pros spin at.