That they don't seems to have as much to do with Android not supporting it as anything. Being able to send messages locally without going through any surveillance checks would be a godsend for protest movements, which may well have something to do with why Google hasn't included it as an option.
It's useful for mesh networking too. We get used to Internet being available everywhere here in places with solid infrastructure but I imagine being able to use ad-hoc would be helpful in a place like, say Gaza. There are tools that help these situations, such as Briar or SSB, but something at layer 2 would allow for a lot more functionality.