Who cares what anyone else thinks? You do your thing, let others do theirs.
Some firms do have upgrade policies, however, and failure to upgrade within a certain time period may be construed negatively or may result in termination.
While you are not obligated to explain yourself, of curiosity, why do you not wish to upgrade? I've met others with the same feelings; they've got what they need where they are, they're senior enough that they get to choose their vacations, their days off, their bids...and they lose that if they upgrade. I'm sure there are as many reasons as there are folks who don't wish to upgrade, or are taking their time to do so.