For companies with massive cultural recognition and trust and product awareness (Netflix, Microsoft, Spotify, etc.), you don't need the app store for discovery or for security.

(Although security is debatable -- e.g. recall the Sony rootkit scandal. I'm still not sure I'd trust a Sony app unless it was vetted by an app store and sandboxed.)

But for 99.9% of the apps out there, this is not the case. The app store provides a lot of value in terms of discovery, security, and distribution. It doesn't do a perfect job, but that doesn't mean it's a "predatory racket".