I can imagine a few good reasons *IF* security is tight enough. For example, many people don't know in advance when they will return home. It might be nice to bump the heat up or the AC down when they're on their way. Some people get 'lock anxiety' when they are out (OMG, did I forget to lock the door). Now they can be sure.
The key is to make sure it is secure. My preference would be a firewall rule on the router that allows me to ssh to a designated box that then allows me to control the home systems. Make it pubkey authentication only.
As for the intranet, given how many people fail to secure their WiFi, I wouldn't count on that keeping it secure either. Better if there is decenty authentication on the device itself.