The problem with that plan is that broadcast radio does not let two stations (in the same general area) share the same frequency, period. So you need to have frequency coordination.
Compare with the ISM bands, like 2.4 GHz, where you can use complex digital signaling (e.g. CDMA/TDMA combined with robust error correction and detection) to effectively timeshare the frequency. The only reason this works well is because the frequencies are two-way and severely power limited - and even then the WiFi channels are congested.
Your home WiFi network has a range of a few hundred feet. A broadcast radio station can easily reach hundreds of miles. The reason those broadcast licenses cost so much is because there's just not enough broadcast spectrum to go around.
A better option for most users is to just stream over the Internet.
(That said, I would certainly love to see a chunk of spectrum set aside for low-power ad-hoc/community stations. But I don't think it would work reliably if it ever got popular.)