There's always someone moaning about this every year. There will always be a lot of singers and dancers. Aren't you used to it by now?
I think generally the public find these acts most appealing and the performances tend to be more powerful and dramatic, so they tend to win a lot of votes.
There are exceptions of course, dog acts are very popular and you get the occasional amazing dramatic act like Alex tonight, but the singers and dancers are never going to be a minority.