How do you know? There needs to be some kind of connection for remote programmability. The default choice is likely something connected to the (W)LAN. From there, it's only one misconfigured firewall and a default password away from being hacked over the internet.
They're not. They've been around longer than WiFi. It's a simple wired connection to the control panel in the tub that's installed as a single unit.
It let's you control things like temp, intercom to the kitchen and so forth. Automatic Bath one of my favorite things about living in Japan, even more so than the heated toilet seat.
I really wish we had decided on Intranet of Things. I don't know how anyone thought connecting to outside services to manage your house was a good idea. Your Own House as a Service, YOHAS. Rolls off the tongue.
Oooh... I stand corrected then. It would certainly make a ton of sense for a bathing culture like Japan, but for showers... eh. Heated seat with bidet and air though? Oh hell yes please.