Some of the best BJJ guys I know started out as wrestlers.
That being said, there are lots of wrestlers who don't embrace BJJ. The reasons are usually:
a. they can't get their heads around being told to relax and not go 100%
b. they can't stand tapping to someone they just held on their backs for the last 5 minutes
c. they roll with smaller/weaker/inexperienced guys who are not able to tap them, and they feel the art isn't all that special
At the professional level, there is no excuse for not having a well-rounded game, and the examples of those who aren't are few. Coleman and Randleman are pretty much the last of the one-style specialists who are so skilled in one area (and so physically strong) that they can still be successful at an elite level. Their time is passing, thankfully. It was seriously painful to watch Randleman just sit there and try to take the pain from Shogun's leglocks, because he had no idea how to escape.
In conclusion, when wrestlers do take the time to change their game and learn BJJ, they become flippin' nightmares. Sometimes I have bad dreams about meeting Sean Sherk in a dark alley. :(