Re: cannot remember what for
Probably to make it go faster. That's what I did on a Commodore PET to get over the atrocious speed of the BASIC interpreter. First I poked a subroutine in what was largely a BASIC program. Then on a more ambitious, machine code only, program it was SYS 1024 and start banging in the hex. The improvement was so great that I had to artificially slow it down to make the game playable. That would have been somewhere in time between the zx81 and the speccy release dates.