you still need to reboot your linux machine or relogin if you updated a process that’s currently running (and in most cases most system processes can’t be just restarted) (…and otherwise you’ll just stay at the old version bit with new data which might cause some instability)
yes, there’s kernel hot-patching but it only affects the kernel, only viable for minor and security upgrades, does not come pre-configured on most consumer distros and not really suitable for home use.