Could that be because the language is fairly young? You don't see the "20-year-old legacy system" in Rust because it doesn't exist yet ;)

And if you look at other comments in this thread, many engineers have this mentality of "just use a crate, it's probably optimised already". They might not have performance problems immediately or obviously but it's more like ten thousand papercuts - a few allocations here and there, a few extra copies here and there and you've got a way slower program than it should have been.