Convenience and being an early adopter are hardly at odds with each other. If anything, these people are early adopters because they want the convenience of not dealing with pc builds. People that already have gaming PCs and love that hobby aren’t going to line up to buy something that they enjoy making, or that they know enough about to feel comfortable buying used from Craigslist.
People are paying for a sure thing. Used PCs and no name Amazon machines are not a sure thing.
You and I might see it differently as people fluent with computers. Reseating a ram stick that got jostled in shipping isnt scary to most people on this site. It is terrifying to most of the world though. Steam is going after people that want to use PC games, but not play hardware tech.