I don't know why the world is still relying upon Bitmain for PSU, If you know the Output Voltage and the accurate polarity then you can build your own custom PSU easily, What is the special about their PSU!
The way these PSUs and the miner itself works makes it hard to clone the PSU, it's a "smart-psu" that interacts with the control board, it's a bit more complex than just a rectifier and a transformer, I don't think it's pretty difficult to do but nobody cloned it probably because 1 it will cost a lot 2 the demand isn't high enough to justify the investment.
I don't think there is any conspiracy theory behind the lack of PSUs, they probably are limited to a certain capacity, I also think they did not expect the failure rate to be this high, most large scale miners I know who bought a dozen of the 19 series said the miner itself is solid but the PSU is trash, so probably bitmain had to replace a dozen of those PSUs and thus they have little to nothing to sell on their website.
Other companies like MicroBT are also short of PSUs, this has been kind of common for years now, it is why one must try to stick to buying the same miner model and get a few extra PSUs for backup, and because most miners die before the PSU does, having the same miner model has a huge advantage over having different models, every miner that dies on you gives you a spare PSU and a control board, I have more PSUs and control boards for my S9s than I'll ever need.
