Sure: They don't, and the people who imply that they do are the idiots.

A full set of ROMsets consists of tens of thousands of archives, each containing a set of files where one file holds the contents of one programmable device: a ROM chip, a GAL/PAL, a microcontroller with internal firmware, and others.

99.9% of these individual sets do not change from version to version.

When a given set does change, it's because a previously incorrectly-dumped chip's data has been replaced by a newer - correct - dump, or a chip that was never dumped previously has now been dumped, or (rarely) the set was renamed.

What you're probably doing is finding full-set torrents per version, posted by some independent group, and assuming that that somehow means that every one of tens of thousands of individual sets within that larger set has changed.

So, hopefully this clarifies which individual is an idiot here.

Just to state the obvious, in addition to correcting old rom sets every MAME release also adds new rom sets for newly supported games (either variations of known games like hacks, prototypes, foreign versions, special editions or completely new work). Typically, there are enough changes to actually disrupt a very large portion of the segments of any full set torrent.