Why is it so? The basic 74 series, the 4000, are such poor ICs compared to the newest families (by the 74: AUC, AUP, ALVC...), which only have advantages over the oldest one: lower power consumption, lower propagation delay...
closed as primarily opinion-based by Trevor_G, The Photon, Voltage Spike, Null, Dave Tweed♦ Nov 2 '17 at 16:04
Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.
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).
5 V logic was "standard" for many years, and there are still many systems and devices out there that need 5 V levels for their interfaces. If you're working with one of them, you need a logic family compatible with 5 V. Maybe not 7400 or 4000 series, but something like ALS or ACT.
Some systems even need higher voltage levels, such as 12 V. In these cases you might still want to use 4000 series logic.
Older families also have the advantage of being low cost and multi-sourced.
Those "fancy" SSI/MSI technologies were developed at the tail end of the heyday of the wide use of SSI/MSI in high-volume commercial products, and were never manufactured in any great volumes. They were not generally incorporated into new equipment designs at the time, because of proprietary and single-source issues.
Microcontrollers, CPLDs, FPGAs and ASICs are the mainstream technologies used commercially today. Only hobbyists are still using SSI/MSI for design, and it is only the older technologies that were manufactured in high volumes (and are still manufactured for older equipment that is still being manufactured) that are generally available to them.
There are a few niche products that are used in modern design, such as the "single gate" logic that's available in SOT-23 packages, but again, because of the packaging, these are not popular with hobbyists.
Cost, availability, multiple manufacturers, simplicity.. are all factors, but I'd argue they are not really that popular any more for new designs. They are still readily available though because they are still used everywhere in older equipment that is still manufactured.
But even today, sometimes it's just quicker and cheaper to plop on a simple NAND gate into a circuit rather than the alternative.
There is something to be said for the basic families though. They are after all foundational to all the higher order parts. You need a decent knowledge of them to really understand the rest so they definitely have their place.