It's against the rules if done excessively and it isn't fun to watch. Ward gets tons of grief for holding excessively. For that matter, so did Hatton. And Richar Abril.

I know I've read a decent amount about Ali holding at least toward the end of his career.

Your examples are odd though because Robinson, Ali and Leonard were holding against Hall of Fame boxers like Jake Lamotta Carmen Basilio, Roberto Duran and Joe Frazier. I like Maidana, but he lost to Kotelnik, and he isn't getting anywhere near the Hall of Fame.