This is just economy question - registers are faster than stack, for similar price. In 80th, transistors on VLSI where expensive, in rad-hardened design where

This is just economy question - registers are faster than stack, for similar price. In 80th, transistors on VLSI where expensive, in rad-hardened design where prohibitively expensive, and stack gives possibility to make same Turing completeness as with many registers command. So some time stack architectures performed well in microcomputers, than their area shrink to narrow-special things, and after many registers become accessible for all, stack architectures become history.