Air quality monitoring stations running at SANAS standards require a lot of regular maintenance, calibration and general babysitting, and that's before you even get the data off them reliably and conduct proper quality assurance on it. The typical station has an array of very expensive and disparate scientific instruments from different manufacturers that all have to be calibrated at least quarterly, the data reliably logged, quality controlled and stored/transmitted.
In other words, a network of air quality monitoring stations requires a lot of planning and management, as well as actual scientific and technical knowledge with site visits to remote and/or inaccessible places - plus you need to have calibration gases in the correct concentrations and the right permits to carry them in a vehicle suitable for this purpose.
In my experience, public sector, municipal and SOE departments responsible for this simply don't have the capability, budget or desire to keep these stations alive, and for private companies it's a huge dent in their bottom line plus the fact that they're often measuring their own emissions is a huge disincentive to actually keeping them running smoothly.
Some of the universities have climatology departments that run air quality monitoring stations but their projects tend to be for a limited time as they are for specific research projects based on whatever funding they get.
If they are serious about this, the only way I see this working in the long run is if there is a central organization that is dedicated to managing a national air quality monitoring network that is well funded and that takes ownership of all air quality monitoring stations, instead of it being left up to whoever feels like making a half-hearted effort at it.