[I_am_uncreative]

They're often performed pursuant to law.

[ars]

That just moves the question to why does the law require it? Just for curiosity?

[SoftTalker]

The law mostly doesn't require it. Only if a crime is suspected, or perhaps in case of accidental death to determine if the accident caused the death or something else happened first (e.g. stroke, heart attack) that lead to the fatal accident (could be very important to determine liability, if any).

But your average old or sick person passing away at home, generally does not get autopsied.

[theultdev]

to ensure or assure no foul play and to keep stats of what's killing us and sometimes try to mitigate those things.

[elzbardico]

For the same reason we investigate plane crashes, to fucking know what really happened. What is a death certificate without an autopsy is just a scratch on the surface. Sometimes we need to go deeper.