One of the biggest ISPs in Germany, Telekom, offers such a model ("WLAN TO GO") since more then 10yrs. It is an opt-in agreement that you can use other people's APs if you also open yours. Many other ISPs offer the same service, for instance Unitymedia.<p>Furthermore, there are popular nonprofits with similar aims, for instance freifunk.net (despite this is not an ISP).<p>Something I would find very interesting is opening eduroam.org for other organizations/private people. It is the worldwide dominating "shared WiFi" approach in the scientific domain.
Charging per the gigabyte is a greedy, bullshit idea that needs to die. It is the whole opposite of "better".<p>This idea of shared Wi-Fi is done by pretty much every ISP out there and nobody uses it for very good reason: it's just not reliable nor performant enough. No matter whether you use Wi-Fi 6 or Wi-Fi 50, you're only getting good speeds with line of sight, low interference environments and good hardware.