The 6502's lack of registers is one point of view.
Another point of view is that the zero page provides 256 registers:
https://spectrum.ieee.org/q-a-with-co-creator-of-the-6502-pr...
"[Bill Mensch]:Rod Orgill and I had completed the designs of a few microprocessors before the 6501/6502. In other words, Rod and I already knew what was successful in an instruction set. And lower cost was key. So we looked at what instructions we really needed. And we figured out how to have addressable registers by using zero page [the first 256 bytes in RAM]. So you can have one byte for the op code and one byte for the address, and [the code is compact and fast]. There are limitations, but compared to other processors, zero page was a big deal."