Sometimes I’ve thought it was because the OP did not seem to think answers written to someone else were good enough and they wanted fresh answers that were just for them.
I used to work with a woman who came into the office a little late, habitually, and went straight to the breakroom. She poured out the coffee in the communal pot and made a new one, even if the preceding one were full and only minutes old. Nothing but the freshest would do for her.
It seems like a kind of entitlement sometimes. That bugs people, even if they can’t put their finger on it.
In reality, of course, there’s often a legitimate reason, but the people who see that are probably not the ones getting pissed off.