If you look at the issue objectively, say as an analyst might, the issue is "beds per night demand." Someone who stops each 15 Km instead of 30 Km, logically "consumes" twice as many bed / nights over the span of their Camino. If you shorten this to only 10 Km walked daily, the bed demand for that particular pilgrim triples from a factor of 1 to 3 over the span of their Camino.
So, I do not disagree with the OP central premise that walking twice as far reduces that particular pilgrim's bed / night demand by 50 percent, etc. However, and this is MY central point, not all pilgrims CAN or CHOOSE to walk that distance each day. Moreover, Camino Rule One opposes this sentiment or judgement. Each pilgrim accomplishes his or her own Camino in the manner they choose. There is no right or wrong, too fast or too slow.
We might disagree with some aspect of how a Camino is done. In my case, I do not see the logic of literally running the entire length of the Camino as though it was some ancient Greek Olympic event. I also have issues with cyclists sharing off road unpaved segments with walkers. But, that is because it nearly cost me my life in 2013 and is a separate issue.
As regards the bicycling thing, there ARE credible and well-mapped routes that are totally on paved road surfaces. Some road bike riders avail themselves of these "parallel Camino routes. Conversely, mountain bike riders remain intent of sharing the path with walkers, mostly to the added hazard and risk to the hikers...but I digress...
The result is that the bed/night demand is what it is. As demand rises across the entire Camino system, either market forces will cause more beds to be brought on line to meet the demand, or the demand on one route may shift to other routes. As the overall, Camino-wide bed demand approaches and exceeds the total bed supply, people will logically opt out of walking the Camino altogether if they cannot find places to sleep. This will be a ways off, but it can happen.
This is economics 101. But, all said, there is another variable affecting this equation...demographic shift...
As the overall popularity of the
Camino de Santiago spreads, and as more commercial entities see it as a product or service to market, we will see a concomitant growth in the number of older persons who have the time and economic means to devote to more casual, assisted Camino.
What these mature pilgrims may not have is the stamina and physical capacity to handle longer distances. This could be for any number of valid reasons, none of which makes their Camino effort any less worthy.
This will only add to the bed / night demand. On the bright side of this variable, most if not all of these commercial pilgrims will likely opt for commercial reserved lodging, in place of albergues. However, THAT is to the detriment of pilgrims like me, who voluntarily opt to stay in hostals, hotels, and casa rurals.
I hope this helps.