I have three axolotl's in the next room, there are no subspecies to my knowledge, except maybe for some cross breeding with Salamanders in the US.
They are common in scientific research as they have amazing regenerative abilities; they will often mistakenly bite each other's legs off as juveniles (they are not the smartest creatures) and then grow them back in a few weeks, good as new. They made it into the exotic pet trade and now they are quite common in captivity, but now critically endangered in the wild. There are attempts to breed and repopulate them, with some limited success.
Another interesting thing, in many countries and states it is legal to keep an axolotl and illegal to keep a Salamander.
They are actually fairly easy to keep in my experience, with two caveats. 1) you need to be able to keep the water below 24 Deg C, this means spending some money on chillers even in sub-tropical countries. 2) If you have a pair in the same tank (regardless of sexing) you need to be prepared to cull the eggs! (freeze them) Prices here went from ~$50NZ each down to around $10-15 each due to the Minecraft craze.
Why are salamanders illegal?
Because they burst into flame! 90% of wizard dwelling fires are caused by salamanders!
(in reality probably the law banning them as pets to protect them didn't include axolotls because the legislature didn't know they existed)
They're either an invasive species, and therefore should not be introduced to the area (and you know that many pets will be introduced once the novelty wears off). Or they're native to the area, and should be left alone because they're endangered or otherwise threatened.
Those are just two reasons, but I'd bet they cover a lot of cases.
Often Axolotls have been "grandfathered" into the legal exotic pet trade, and salamanders have not and they tend to be considered separate species, even though biologically it's a very blurry line. Also, it often happens in areas where there is a local wild salamander population that is being protected from poaching.
You likely don't have wild axolotls nearby so if a pet escapes it'll just die and not affect the ecosystem. OTOH, an escaped salamander might thrive and displace wild salamanders and disrupt the ecosystem. Or carry a disease, or ...
most places ban exotic pets that are able to survive in the local climate to prevent invasive species from outcompeting the local feral cat population.
my understanding is that thr light skinned / pink variants are the results of mutation and selective breeding - and obviously racism, light skinned being considered more cute - in the pet population and almost all examples in the wild are dark skinned.
Racism? Come on. A camouflaged pet you can't see in the tank isn't as fun as one where you can see all the crazy physical structures.