It's not banned, they're forcing the Chinese to divest ownership & control of it, same as China does to US companies, really. The fact is that they'd rather shut it down than be unable to gather location data or build social graphs of their user base.

Frankly the propaganda aspect is the least troubling part of it because you're right, people can make their own choices about information sources.

But figuring out who various military members are connected to, where and how they're moving around, and especially any leaks where people take cell phones in places they shouldn't (remember that ship that installed a Starlink illegally?), they can get quite a bit of intelligence.