Because that’s exactly what Bluetooth is. Bluetooth uses a very weak radio signal that can only travel about 30 feet and is easily blocked, which is precisely why it’s available for open use and not a limited use/licensed frequency. It’s available to use freely for these short-distance communications precisely because there is little practical use for it otherwise and it’s too weak to wreak much damage if someone tries to employ it inappropriately.
The problem isn’t with the pump being more weak or defective. It works exactly like your cell phone and receiver do to communicate with the transmitter (sorry @MM1, but all the talking is done via Bluetooth, even to pump and receiver). The problem is with the close proximity and all the possible interference the signal can face trying to get from one place mounted on your body to another place mounted on your body. There’s a lot of chance for something to disrupt the signal. This is one of those problems that largely goes away once the pump trains you how to place things happily. Moving the pump away from our lumps, bumps, curves, and miscellaneous interfering appendages will actually improve connection. The pump trained me to put it on the bed next to me at night, rather than attaching it to me, or else I get dropped communication alarms. I don’t know why, but I’ve never seen much of a problem with this during the day.
The one thing Tandem could do better is rearrange some internal components so the Bluetooth antenna isn’t behind the screen. But I think that’s one of those, no win situation things. My perfect wear placement requires the screen to be facing me, otherwise I would look like Ironman all the time with a brightly lit chest bulge. But that’s just how I like it, I’m sure it’s a 50/50 split on directional preference.
@MM1 had a great point about not being able to use both the pump and receiver, though The G6 can connect to one primary medical device (pump OR receiver) and one secondary device (smartphone or standalone watch mostly). If you’re trying to use BOTH the receiver and the pump, they’re going to fight one another and the information will only go to the strongest connection.