Because here's the thing: just because I enjoy something doesn't mean that it is "good" by any metric except the "does Ariela enjoy it?"-o-meter. I enjoy some things that I recognize as being bad by any number of metrics. Candy corn, for example, is terrible for you, and not actually that tasty, I just love it. I also hate all coffee, even high-quality coffee; my lack of enjoyment of anything I have to put in my mouth that includes coffee says nothing about how good a product it is. There are also things that I enjoy that are good, like a perfectly cooked meal, and things that are bad that I don't enjoy, like undercooked chicken.
So, too, with media. I enjoy some horrendous things, and there are some things that I recognize as being superbly skillfully done that are just not my cup of tea. And when I vote for the Hugos, I am trying to indicate that I think something succeeds in the metrics of innovation, craftsmanship, skill, and execution. It's not really about what I liked, it's about what I think exemplifies everything I want to see in the field of Spec Fic. And yes, we can - and do - argue about what the field of Spec Fic should be. But anyone who thinks that the field of SF should consist of only what they personally enjoy, with nothing for anyone else, is probably not worth talking to.
I want there to be SF for people who like things that are dramatically different than what I like, and I want the offerings for them to be good. I want them to have things they love, things that speak so deeply to their experience that fandom becomes part of their identity. Just because I don't share it doesn't mean it shouldn't be awesome for them. I also want good reading and viewing options for me, and I hope they would support me in my desire for same.
So, for me, the Hugos are not about voting for the things I enjoyed the most, they are about voting for the furtherance of the genre.