I'm presuming no UX team anywhere has stated "We're done here, there's no way we can improve on this UI". Hence to keep busy changes need to be made. Same with Health and Safety requirements, once a team is in place H&S 'creep' is inevitable. I once worked on a risk assessment for a laminator.
Good UX members won't stick around if they believe something is finished. But someone above them is always mucking something up, so there's always a problem to solve.
