The vast majority of newer vapers are not interested in rebuilding. Heck, most don't want to have to change a replacement coil head in a clearomizer or replace a cartomizer in a cartotank by comparison. Most want something that was as easy to use as a cigarette.
Rebuildables are fine and dandy if you like to tinker and fiddle with your gear. I've given them a nice fair shot myself. Sometimes they worked great, sometimes not so great - they required the tinkering, fiddling, and time I'm not interested in doing. I watch in amusement the rebuildable enthusiasts at my local vape shop. They seem to never be satisfied with their "builds" and often redo them every 2 - 3 days. Maybe they are just perfectionists, but that's not what I want to be doing. I just want to vape.
Rebuildables took me nearly a half hour to do a new build. Cut, oxidize, and roll the SS mesh wick. Oxidize and wrap the coil. Measure the resistance. Pulse fire and check the coil for shorts. Prime the wick and do more test fires. I'm sure with more experience the time would become shorter, but that's still more work & time than I'm willing to put into my juice device.
By comparison, I get a wonderful vape from my cartotanks. Excellent flavor and vapor; not the clouds one can get from a rebuildable, but that's not my ultimate goal. I want something KISS (keep it simple stupid). I spend 6 minutes setting up a new cartotank, and the only maintanance thereafter is refilling the tank for the next 2 - 3 weeks. Change the carto with a primed carto and I'm still good for another 2 - 3 weeks.
Rebuildables are only popular with the enthusiasts who frequent e-cigarette forums or vape shops, and even then they are a subculture of that subculture. By comparison they are but a fraction of all vapers. Rebuildables will never become mainstream. It will always be a subculture interest.