I see it as a hassle- I dont want to be doing a bunch or redundant whitelisting to make the percona tools work. Worse, I don't want to ship them separately, xtrabackup uses mysql as a library, which means separate containers only buys you bugs.

Docker's design decisions make sense if you're shipping statically linked, standalone binaries everywhere. Which I suspect docker.io and many other people are doing. But that's also sort of a boring edge case where you don't even need filesystem namespaces except for cleanliness.