I've noticed in some threads that some people are always thankful that Chuck is very low in the mix which leads me to think a couple of things:
1. People don't like pianos (keyboards, organs whatever).
2. People don't like the fact that a lot of Stones songs have piano/keyboard parts in them.
3. People don't like the fact that Chuck plays on some songs and is somewhat high in the mix.
As for me personally, I don't mind some good piano (the late Ian Stewart was definitely the man for this, as was Nicky Hopkins) but I can't stand the fact that some piano has been included in some songs like Start Me Up. There's no place for it, especially in that particular song imo.