I would think it's a pretty small minority who likes to deal with it?
Hmmm... kind of a two-parter.
Kanthal, I would think, is the dominant choice for building coils these days. The majority of rebuilders would use it (I do).
Silica, OTOH, is maybe declining in use. Cotton seems to rule the day, particularly with the microcoil crowd (building a micro and annealing it is easiest without wicking material in place, and cotton is very easy to work into a coil once it's twisted and mounted). Myself, I've moved on to bamboo thread. It gives me the control of silica (discrete threads to work with instead of an arbitrary mass of material) and the flexibility/ease of cotton.
No doubt this will all change as vaping techniques continue to evolve.
Now, as to the percentage of overall vapers who rebuild with anything, that's a good question. I suspect the market is growing at both ends - mass/broad/convenience at one end, advanced/tuned at the other. I'd bet on the carto/clearo crowd using an ego or provari/vamo/zmax/mvp to become an even more dominant majority as vaping progresses through to being ubiquitous.
I would think it's a pretty small minority who likes to deal with it?
I make coils, the wife doesnt... so Id say 50%