For me, it's twofold:
1. The Roth conversions, as previously mentioned.
2. The belief that Medicaid was founded to help people who could not afford healthcare. I don't want to take a slot from one of them, or use assets earmarked for them. So yeah, it's partly a moral thing for me. Just because I could finagle the numbers to work doesn't mean it's fair to when I'm sitting on a decent stash.
However, as ACA exchange plans become sparser, more expensive, and less appealing, I must admit I'm looking at Medicaid as a potential option someday. I wouldn't do so if I weren't worried about skyrocketing healthcare expenses with no clear signs of settling down or even predictability; I don't want to lose my hard-won stash to some freak accident or medical emergency and end up on the street. It's also why I'm considering relocating to a country with universal healthcare.