You still have at least 1 other live opponent to try and take chips from so why would you rule it out 100% ?
Keeping in mind we're talking about a hypothetical which doesn't crop up very often at all, if the locked main pot is small and you, along with the other live opponent(s), have much larger chipstacks I see no reason to not attempt to build a larger overall pot for yourself - IF that's what you decide to do based on whatever other factors you wish to consider at the time.
I'm sorry but "the side pot is dry" just isn't a good enough reason to play differently, if that's the only reason present. It's equivalent to saying "I will check because I know you want me to" and if I know someone wants me to check in any other situation, damned if I won't be betting just to stick it up them

