Jennifer Ouellette scours the science:

People like me just lack certain key taste receptors, preventing us from appreciating the rich, sweet, meaty flavor of raw tomatoes that the rest of you are always rhapsodizing about. The problem is that tomatoes have something on the order of 400 volatile compounds and who knows which one of those (or combination thereof) might be responsible for the harsh reaction many of us experience in response to raw tomatoes?

It may be the same reason some people hate cilantro: