This is the default setting for Debian/Ubuntu, and also Arch Linux kernels. If you don't have a need for that setting, (eg. running Docker commands without sudo), you should probably disable that anyway.
But also e.g. by the chrome sandbox used by e.g. electron apps (or e.g. 1password). Through that sandbox helper binary can also work with being a suid program.
I also wouldn't be too surprised if e.g. proton will start using user namspaces at some point in the future.
So for any non-hardened desktop linux system you probably should _not_ disable it!
(For many servers or special hardened Linux it often isn't a bad idea to disable it.)
the problem is that containers require tons of hacks on the network side to just-work. and docker main selling point is all the usafe hacks it does for it.
so obviously, any container solution will adopt these hacks eventually, and there is the problem.
you end up with a perfectly sane namespace functionality that removes access, but then the kernel opens the gate because network hacks are good
also people focus on this only being a problem now with priv escalation... but all that was always a problem before unprivileged containers... by allowing container code to exploit host kernel code, but nobody called it a privilege escalation then because you started your container as root. sigh.