I mean, if you could download an update that would fix the wiring in your house, it would be much less critical that the initial installer got it right. (Still much more important than your router, though; it doesn't stop being an electrocution hazard during the un-updated period.)

Trying to make analogies from software to hardware will always fall down on that point. If you want to argue that there should be stricter security & correctness requirements for routers, maybe look more toward "here is how people actually treat them in practice" with regard to ignoring updates...?