I think in many cases there's a mismatch in 'expectations management' that causes burnout in maintainers. Once a project grows in size and popularity the dynamics change to a large extent. And if the maintainers don't deal with that they'll see the burden and the expectations grow and grow.
Entitlement may be false entitlement in their eyes, but users on the other hand also 'invest' by using the software. In part it is communication mismatches that cause things to go awry.