Good question - in my experience, the proposer does not often change the default gas limit, which is typically set to 30_000_000.
However, anecdotally I have observed a greater proportion of parent blocks with a different gas limit. There can be many reasons why, but one possibility is that other block builders are proposing blocks with a different gas limit than what the proposer set, causing greater fluctuations that lead to proposer’s gas limit being rejected from exceeding allowed limits.