Personally I don’t see any harm in asking people to vote, as long as it’s not incentivised which would IMO be unethical and also cast a shadow on the validity of awards. Some awards have become a joke because everyone knows that people have been offerred incentives to vote, or the winners turn out to be big advertisers.
Take the William Hill “Best Support” award back in London in January (forget who awarded it but it wasn’t CAP). Now Will Hill are good at a lot of things, but anyone who knows anything knows that their support isn’t one of them! We had a good laugh about that one in the pub one night 
Also, Intercasino used to offer players bonuses to vote for them in the Gambling Magazine awards. Now as it happens, Inter is a very good casino and they may well have won it anyway, but when word got out, the player forums had a number of threads that basically questioned the validity of the awards, the upshot being that a lot of players had no confidence in them.