Not every user is smart. That's why there is a necessity for centralized/trusted solution. I wouldn't sleep well if I knew my mom could install a malware by mistake on appstore. Unfortunately, life is not this simple and every path there's a toll.

The problem wasn't that we didn't have decentralized solutions since the 1960s -- it was that we've never figured out a way to make hosting your own environment as easy / cheap as using an externally managed one.