The normal progression is that you had a commercially built one, and one of two things happened. 1. It was a prebuilt FPV drone and you need to repair it after smashing it into something at mach Jesus or 2. You bought a DJI, which is really a camera platform, and you want a drone that can fly at mach Jesus and do the cool aerobatics so that pulls you into the FPV genre where you buy a prebuilt or just build from scratch.

Drones are just an example, there are plenty of other areas where people might get sucked into DIY electroncisbuilding. E-skateboard/bike/scooter modification and fixing, keyboard hobbyists, cosplay, 3d printing, home automation etc...