Should removing old kernels trigger the "reboot required" message?

[Adam Funk]

I was just using apt-get and did `apt-get autoremove` as recommended
to remove an old set of kernel packages (linux-image-4.8.0-44-generic,
linux-image-extra-4.8.0-44-generic, linux-headers-4.8.0-44).  That
still leaves the 4.8.0-45 and 4.8.0-46 sets installed, and the system
is running -46 already (I rebooted after apt-get installed it a couple
of days ago).

This has set the reboot-required files:

$ cat /var/run/reboot-required*
*** System restart required ***
linux-base

So I know that next time I log in (GUI or ssh) it will tell me it
needs a restart.  I can't see any reason why this is really necessary
after removing a kernel that wasn't running, so I'm in the habit of
deleting those files in (only) this situation.  Is that harmless?  Is
there a good reason why the system sets the reboot files in this case?

(I can't be sure, but I'm under the impression that Ubuntu hasn't
always set the reboot files in this particular case --- I think it
started in the past couple of years.)

Thanks,
Adam