Generally DJ's who do it for the money only, so that would rule out 99% of DJ's on the soul scene.
I thought I'd give DJ'ing in bars a go, about 5 or 6 years ago, so I bought a load of commercial tunes, mainly the shitty MTV r&b type things, because I knew that's what would be required, but I HATED doing it, not just because of having to put up with the brainless pissed up dickheads and arrogant bouncers strutting around the place, but mainly because I couldn't hack playing music I didn't like, having only DJ'd on the soul scene playing music I loved to people who in the main felt the same way.
The majority are collectors first and DJ's second, anyone can stand behind a set of decks playing music, anyone, but it does take a degree of talent to be a GOOD DJ, rather than just having a good collection to draw on.
Imvho of course.