Please correct me if I'm wrong but is that not also the case for the Albergues? As I understand it the various regional bodies , townships etc take care of their own, to the benefit of not just the pilgrims but of course the local populace. And of course, a few volunteer organizations and so forth - such as those you yourselves have worked for.
It has been pointed out elsewhere that without the pilgrims some of these little townships would have died out. At the very least pilgrims, and the business they bring, have certainly revitalized them.
The cynic in me says it's because toilets don't directly bring in money.
As a man I do not NEED a toilet as frequently, however as
@Trish1Corless says above, when I do I would happily pay for the privilege. (Should a bar not be nearby - I do love my aquarius and cafe con leche!).
Presumably once the initial build costs have been overcome, 1/water, 2/toilet paper and 3)cleaning/maintenance would be the biggest issues.
1/There is a vast array of high quality well priced composting toilets out there nowadays. No water required.
2/ restocked every time the toilets are cleaned with the typical public toilet rolls. Yes they'll run out occasionally but most of us with any brains carry some toilet paper or worst case tissue. (Which doesn't compost as readily and often comes in nasty little plastic packets, but that's a different issue).
3/ the €1 fee would cover most if not all of the costs. Even allowing for some cheating of the system. Cleaning frequency would of course vary based on route and the number of pilgrims.
Building and maintenance of them adds of course to the local job market. A win for everybody.
Based on the numerous posts on this subject it will be very easy to identify the prime spots for these toilets !