Some people are inherently hands-on. They like to feel objects, manipulate them, work them. Especially household machines. But dealing with torsion springs in a garage door can be a bit more dangerous than most are used to. A basic roll-up garage door may just be one of the hardest things in your home to repair.
There are a lot of great things that can be said for doing things yourself and being self-sufficient. But your desire to do things on your own terms may, in the case of garage doors, be thwarted by the system that's in place. Commercial sellers of individual parts are not interested in selling you small pieces- they want to charge you for the whole kit and caboodle.
Manufacturers and most distributors of the springs are under the impression that it's to their advantage for to directly retail products to the consumer- they can charge more by restricting supply and dealing mostly with repair and installation companies. Technically, restraint-of-trade agreements are again US business laws, but its hard to successfully navigate the intentional roadblocks that are in place. In fact, there are many areas in this ocuntry in which garage door products (especially dangerous ones like springs) are licensed trade. This often leads to situations like monopsony and monopoly, and market fialures.
For example, most of the springs in garage door maechanisms operate using torsion, which exerts a lots opressure on the steel. these springs then only last about 10k lifts. That means, if you open and shut it four times every day (one for getting in and out, per trip) then that means your garage door will only last you about seven years, give or take. therefore, its practically a guaranteed that you'll have to have the door repaired at least a few times over the life of your home.