Not entirely sure why more people on a camino is positive, for some the quite less used ones are the most attractive purely because there are less people.
Well, Stroller, I think that the main positive is that unless a camino reaches a critical mass, the private initiative to build albergues (and other services for pilgrims) will not materialize. Right now on the Invierno, there are only two pilgrim-specific albergues, and they are about 12 kms apart from each other. One town, Pobra de Brollón, has responded to the closing of the one private place in town with an offer of the sports center for pilgrims and plans to build an albergue, so it it happening slowly. There is lots of talk about opening albergues along the way, but until the pilgrims materialize, the real push is not there. The proverbial chicken and egg problem.
Fewer people is great, no people is too lonely for many. I know there are a few of us who relish walking caminos where we sleep alone and meet no one, but as someone who has walked the Invierno several times, it would be great to meet a few others along the way. And from the vantage point of all these dying villages, the camino very much seems like a great opportunity for revitalization. Of course, to use another egg metaphor, it’s like the goose that laid the golden egg — how can you get to that magic “just right” number of pilgrims without the massification that makes people search out these untraveled caminos in the first place!