The answer is life, and time. People want to do these things, they start them, and then stuff happens. They get a job, a girlfriend and then suddenly find they have zero time to make games because their entire life is already taken up. They desperately try to find time over the course of several years but they barely make any progress. Next thing you know it's half a decade later, the programming language they were building it in is no longer relevant, most people have moved over to mobile phones instead of pcs and they'd have to start from scratch a project they dont even have time to keep working on in the first place.
