Why does find my iPhone need internet?

So i've had this burning question about these programs that are supposed to recover you're phone. From what I've seen they all require an internet connection so that they can send the request for the phones location, or to tell the phone to set off a siren or lock.

The problem is that, for me at least, I never leave my Data or Wi-Fi on when I'm not using them because they burn through the battery. So if i were to lose my phone it would most likely not have internet… At which point I would just be "up a creek without a paddle."

Why don't they just like communicate with cell towers like regular calls, or use text messaging, I'm sure there's some way they could rig it so that the their doesn't know you're locating the phone. Just so you could send the signal to the phone to let it know to start locating itself so it can send it's location back to you, or set of a siren etc.

is there some good reason they don't do this? Or do they do it and they just don't tell you… I'm confused.

Because this is a consumer feature. To track a phone using the IMEI number (non-internet connection) you'd need to be a member of law enforcement or government. This is for privacy reasons.