Where ?
Like Steve Cato, I've done over fifty spots in the States, France, Germany, Italy, Holland, Ireland, and never, not one single time, have I seen anyone DJ using MP3s.
OK, some of the guys in the Modern Rooms use CDs, but they tend to be individual artists CDs with the track they want to play rather than a compilation CD from Tesco, but certainly every event I've attended outside of the UK has been original vinyl only, and the promoters of those events wouldn't want it any other way. (And it's Modern Soul so that doesn't count anyway )
So, please clarify which events you are talking about.