Why are old digital ICs families still so "popular"?
Why do you think TTL 74/54 series are popular? They are a relic of the past now (unless you have to maintain old hardware).

Metal gate CMOS 4000 series is also somewhat obsolete, but it has some advantage in some specialized digital application where its wide supply range (up to 15V at least) is convenient. Of course it's slow and power hungry, compared to newer CMOS families.

74HC/HCT is mainstream because it is mature and stable (but it's losing terrain).

The other, faster, families are used only if you really need their speed. A faster digital device is not necessarily an advantage in a circuit that doesn't need that speed.

If you are a student, I suspect that your intuition is skewed because many high-school labs (and even university labs) purchased tons of TTL (and CMOS 4000) chips and many teachers love beating a dead horse (sadly).