There is a lot of things we need to keep up to date. Almost every appliance today has some sort of software running it and more and more of them are also becoming connected.
It's not about getting the more up to date, more stable version of the firmware on those devices. It's not even getting some new features which almost justifies the ability to update versus being reliant on something like that.
It's all about security. Every device can be attack vector to breach your privacy. Sure, nobody is probably that interested in your privacy these days to go through the effort infiltrating it through these devices. Those things are available on the internet anyway at much easier reach.
The main use of such breached devises is to use them in some even more malicious coups. Harvesting the computational power and network bandwidth can be used to launch much more dangerous and lucrative attacks.