The thing is it's not slow because rust is doing anything wrong or unoptimized, is slow because cleaning up insane amounts of memory allocations is slow.

Also if you run this:

``` fn main() { ::std::thread::spawn(move || { println!("end")}); println!("Hello, world!"); } ```

You might notice that "end" might not be printed because the main thread exists before it prints and terminates the process. This means that the dropping might actually not happen if it's at the end of the program and nothing is faster then not doing the work.

Also it's a not uncommon pattern in small user facing CLI to leak (memory) resources, as they (should) be cleaned up with the process termination.