Re: I never see my bees pollinating my garden plants.
Most likely your bees have found plants outside your garden that they prefer. As far as tomatoes go, this may be helpful:
I was surprised to see bees working my asparagus pretty hard a few weeks ago. The blossoms are very small and plain, but clearly they have something the bees like.
ultracrepidarian >> noting or pertaining to a person who criticizes, judges, or gives advice outside of his expertise