Think of it this way - Megacorps once upon a time realized they had a lot of lavatories not really being used. So they decided to start renting them out. That became a profitable business. Thanks to how Corporate Robots are programmed, the moment a profitable business is spotted, the next move is to Scale up.

They got a bit carried away thanks to Moores law making lavatory building cheap, especially if you buy a million at a time and so now we have town sized constructs of just lavatories. And all those lavatories need infinite quantities of piss and shit to justify their existence. Conduct hackathons. Fund incubators. Hire the best and brightest and it's possible to get populations to ramp up piss and shit generation. It then takes armies of sales and marketing drones zigzagging the planet day and night incentivizing orgs and people to ditch their own loos.

The stagnating transport industry (Big Telco) woke up when they noticed people taking shuttles to Mega Loo Plaza and started competing with each other to upgrade their own transport infra all over the world. A confluence of all these factory take us right back to where we started. A lavatory excess. But don't worry the Corporate Robot class is on the case. The goal is to get people to piss and shit 24x7 to utilize that excess (you will notice people who produce a lot piss and shit are encouraged). And things seem to be going well.

And ofcourse you can use your own loo at home. They are very cheap these days.