How many other's would be willing to buy locomotives and train cars in kit form , if it saved money? Think of the old Athern HO scale blue box kits.
Sure. Most of the "younger" crowd probably won't go for this as they want "instant gratification". We run into this mentality in the RC airplane hobby. ARF's are very popular buy you can't hardly sell a kit anymore.
Athearn discontinued kits, not because of popularity, but because with the extra staff/cost needed to handle missing/broken parts. Between having a customer service person to handle the calls, keeping an inventory of spares, and the cost of shipping/handling those replacement parts, kits were costing them more to make than the RTR cars. When an RTR left the factory, in theory it wasn't missing any parts.
RTR was cheaper and easier for the companies to deal with than kits.