If the kernel, initramfs, or a driver is updated, you have to reboot the computer to apply them (you can't reload the kernel while it's running). A user might not know or notice this, so GUI installers (and some CLI tools like pacman on Endeavour) often warn the user or sometimes force a reboot.
Well, then I don't understand the downvotes, lol. The person i replied to said sometimes a distro will force a reboot, I said that's bad, and a bunch of people apparently disagree with that.
Those distros "force" you to reboot when you want to update (as opposed to allowing you to do the update on the running system). Think Windows 7 and earlier, that kind of forced reboots, back when people were fine with the way Windows did updates.