I'm not sure if it's a correct impression but my impression is still that AWS is the "devil you know" and Cloudflare is less predictable with more individual decision making from high ups.

I guess they got that reputation years ago when the founders (?) got into public spats about what they would and wouldn't host. AWS is more lawyers and committees and seems more anonymous, so people don't necessarily like it more but they do trust it to be what it looks like more.

Probably just a function of time and size.