I think they really should charge with micropayments, and they could even roll out their own currency for that if need be. Ads suck.
Actually, all the AI companies together should choose a micropayment system to focus on. I know in fashion, I've seen what would seem like competing brands center around a common "pillar of influence."
Also, if (long-tail?) AI companies work together, they could install appliances and terminals around cities. The most immediate use case - transport timetables. It seems like a no-brainer the more I think about it. Especially good for tourists who don't speak the local language. Governments may end up wanting to do that anyway and could subsidize the cost. It really depends on how fixated people are to owning their own screen, versus using someone else's. Those city screens could end up billboards anyway - especially for local businesses. They could print for a fee too and third parties could pay to get their app listed. Also, it's worth considering the increase in wealth inequality and rising hardware costs for people to own and stream into their own device. So this could be like the Internet Cafe 2.0.
Incidentally, there's a recent thread about someone streaming HN to a cheap display: https://news.ycombinator.com/item?id=46699782 - why not have such displays around town? I guess one major problem is vandalism.
People have been suggesting a micro payment system for the web for over a quarter century
https://www.w3.org/TR/1999/WD-Micropayment-Markup-19990825/
Why would you want to use a terminal for mass transit instead of your phone?