That's fair, but even interesting graffiti still won't let any sunshine come through. Also, I would rather look out the window [0] than appreciate artwork when riding on a train.
[0] https://www.swr.de/swraktuell/rheinland-pfalz/trier/17134459...
[0] https://www.swr.de/swraktuell/rheinland-pfalz/trier/17134459...
It's far nicer and more interesting than yet another development or parking lot.