Why does it seem like most autopsies are done purely for curiosity, without any actual benefit to anyone living or dead?
Many of them are performed because they're required by law, to establish a cause of death both for the families but also potentially to understand if someone else was responsible for the death.
Many of them are performed because outside of the above, we have historically learnt an enormous amount about the human body through studying them, particularly for unique injuries or illnesses.
Otherwise, there are many that aren't performed at all
But your average old or sick person passing away at home, generally does not get autopsied.