The wifi isn't there for the firmware, it's there for the wifi functionality (Don't ask why it needs wifi functoinality, I can't answer).
But once you do have wifi functionality so you have wifi hardware, then the thing needs patching and upgrades too. Maybe some server address has changed, maybe a security fix, etc. And obviously if you have wifi hardware, it's the easy way to upgrade the software.
So the question I think isn't "Why does the firmware need to be updated at all"? It likely wouldn't, if the firmware just made the machine clean dishes. The question one should ask is, why does it have network features at all? What possible use case can exist?
Precisely. The reason it needs a firmware upgrade is that the manufacturer made the choice to make it so needlessly complicated that it ... needs a firmware upgrade.
But once you do have wifi functionality so you have wifi hardware, then the thing needs patching and upgrades too. Maybe some server address has changed, maybe a security fix, etc. And obviously if you have wifi hardware, it's the easy way to upgrade the software.
So the question I think isn't "Why does the firmware need to be updated at all"? It likely wouldn't, if the firmware just made the machine clean dishes. The question one should ask is, why does it have network features at all? What possible use case can exist?