If it's a USED but NEW to me I do a fresh install. Long ago, I used to replace the HDD completely.
But if it's a New new Mac there's no reason.
If it's a new OS that has big changes (such as Big Sur) or if I was moving to a different CPU platform (PPC-Intel, Intel to ASoC, or Intel to AMD) I'd back up the machine, wipe it clean, then migrate the apps and files back over slowly.
I didn't do that with Big Sur for my personal machine, thought it wasn't a big deal, but now half my extensions and about 7 apps and games don't work.