You have very limited experience with recreational divers then who use higher O2 content mixes for dives.
AN is not strictly for staged decompression dives. It can be and is used by recreational divers on dives who do not do required stop diving.
I know a number of recreational divers who will switch to a higher O2 for their ascent and safety stop. One who is older and took a DCS hit. He does this as a precaution now.
If the AN course is taught properly it includes a great deal of theory and tech diving philosophy that should be applied to ANY deep dives.
While AN does not require deep dives, it does provide a much more solid foundation in diving period than the average deep course. Buoyancy control, trim, rescue skills for O2 toxicity hits, gas management, dive planning, and use of a deco/stage bottle. In the AN class alone like this they would get 6 hours plus of bottom time drilling on skills over 5 dives. Then the DP class was a minimum of 5 so the combined course was 10 dives.
When I taught AN I found that students benefitted from taking the AN course then doing DP a bit later. This gave them time to work on their team skills with multiple bottles and refining their drills and planning procedures.
It was also less physically and mentally tasking so they absorbed more and were in better condition to do the dives.
When it came time for DP I had a solid team who needed no remedial time and we could get right into the DP skills and dives.
I've had students take AN with me and follow up with DP with another instructor because they could do it in a warmer location than I offered. Or because they wanted to switch to a higher O2 for the end of the dive. And at least one who was going to have to wait for DP at a later time because of finances. Which is perfectly fine as well.
To say AN by itself is worthless is narrow minded and uninformed about what a good AN class is and what mixes higher than 40% can be used for.