As I understand it, the idea is that people are essentially subletting the bandwidth they pay for from their ISP.
ISPs famously overprovision users. While your ISP plan may nominally guarantee some level of bandwidth, the network physically can't support all users using that much bandwidth at the same time.
It's like gyms where if everyone who had a membership actually showed up, there wouldn't be enough gear to go around. The gym's business model completely relies on the fact that most members don't use the maximum of what their plan allows.
ISPs don't want you subletting their bandwidth because that makes it easier to consume all of what your plan allows. They absolutely can't handle a signficant fraction of their users doing that.
So, if a subsidized mesh network were to ever become popular enough to be a viable business, ISPs would simply forbid users from participating in it.
It's just a fundamentally broken business model. It would be like sharing a gym membership across multiple people. Makes perfect sense for the member. "Hey, I only go one day a week anyway, so I can let 6 other people share it on the other days!" But the gym itself straight up could not sustain that at their current membership prices. Their only options are:
1. Forbid it (which is what they already do, since membership is associated with a specific person).
2. Go out of business.
3. Jack up membership prices until they can sustain all members fully utilizing their membership. But that would drive away members who didn't share memberships and make it so that your fraction of a shared membership is about as expensive as a single one used to be.
Fundamentally, you can't pull infrastructure out of thin air. Pretending you can be reselling it won't work.