Note that it appears there is a 100 registration limit per Google account. And each factory reset changes the ID the phone is registered under. For a lot of ROM folks, this is probably not going to last very long.
It was annoying to have old dead devices still on my account with no way to remove them
I suspect there'd be bursts of burning multiple in a single day, for what it's worth. People flashing a phone, realizing something isn't working after they set up their registration again, and having to flash again.
So, yes, people absolutely do.