I don't think he was asking what the benefit of remotely accessing sensors and the like is. I think he was asking why on earth they should be on the internet. Which, I think, is a valid question. The internet is far from the only way to accomplish that, it's just the most convenient -- if you don't care about security at all.
If you really have to have this stuff on the internet, then you also have to engage in quite a bit of security groundwork for them to even begin to approach being something reasonably secure, which takes away a fair amount of that convenience.