...If you're using the alloc/std crates (which to be fair, is probably the vast majority of Rust devs). libcore and the Rust language itself do not allocate at all, so if you use appropriate crates and/or build on top of libcore yourself you too can have an explicit-allocation Rust (though perhaps not as ergonomic as Zig makes it).
I mean yeah, allocations. Allocations are always explicit. Which is not true in C++ or Rust.
Personally I don't think it's that big of a deal, but it's a thing and maybe some people care enough.