Money doesn't work that way though. There are plenty of jobs people would like to get paid to do, that doesn't mean someone needs to psy them to do it.

I'm well aware that if at some point AI is good enough to replace me as a software engineer then I won't have a job. I don't expect a company to continue to pay me simply because I enjoy it if there are cheaper options out there.

Math is no different.

This is really the critical thing: the fun is the incentive. (Or at least the dominant incentive in math, historically.) As economists like to say, the overarching lesson in economics is that incentives matter. Reduce the incentives and participation will decrease.

Perhaps that won't matter if we enter an era where AI participants are the main participants who matter for discovery-level mathematics. But it would likely be what economists would see as a market failure if only a small oligopoly of AI participants, closely held behind closed doors, is able to fill that intellectual role.