This is more related to the fact that computing systems are usually preemptive multitasking systems that are expected to operate very predictably even with stuff happening in the "background".

If you really want or need reliable timers or miss those days for any reason, check out a Real Time OS.

That's basically what `timer_settime` does if you have a realtime scheduler.

People sleep on /dev/rtc and PIE !

.. or the MSDOS/PC timer interrupt at something like 15Hz?

https://www.xtof.info/Timing-on-PC-familly-under-DOS.html (wow, this is more complicated than I remember)