the radios are cheap and work incredibly well

But they're proprietary. Which is bad.

Edit: and to be clear, it's not just that the radios are proprietary black boxes, which is bad, it's also that by using them, you make it necessary for all other parties you communicate with to use matching proprietary black boxes, which is bad squared.

there isn't much of a reason for someone to homebrew their own

Especially when there's an existing, open standard for communication using the same principles.