[andor]

But you’re not carrying around your own water treatment mechanism either (unless you’re out hiking). It is relatively easy to install air purifiers or UVC lights in offices, schools, grocery stores, etc. The problem is that people don’t care enough about air quality and the ROI isn’t clear. Increasing the ventilation rate in an overstuffed co-working space has cost implications for the operator, but it doesn’t increase revenue.

[lazyasciiart]

The point is that if you don't install pipes, there's no water going into the house, and so pipes were created even before water was being treated, and it made an easy single point of control. Air is arriving everywhere from everywhere - there is no existing system that can be monitored and set to improve it without every house updating.