Yeah, and? I have that goal as well! (But to be clear, I don't like you're phrasing, but I get your drift.) This very thing is a large part of why I go out and library-ize a lot of the code I write. Some day, maybe those shims will become library-ized and others will be able to do what ripgrep does without needing to rewrite those shims. I see no reason why this cannot be done. I see no reason why the Read trait isn't composable enough to build that kind of infrastructure. I see no reason why memory maps couldn't be made to work correctly on 32 bit systems if there is demand for it.
Like, we get it. You're unhappy because your favored abstraction hasn't been built in Rust yet and library-ized. You've made your point. The next step is (for someone) to prototype it and solve a real problem that folks care about with it. This navel gazing is pointless IMO. I tried to tell you this a dozens of comments ago.