If you wanted to, for example, write a new experimental functional language and reuse part of the Rust compiler to sanity check and generate the executable, then tail-recursion would be really important.
Similarly, if you create something like a parser generator and don't have tail recursion optimization, then you are going to run out of stack space before being able to parse stuff. So, there are lots of practical applications that depend on this feature too.
Maybe the author wanted to say that Rust (currently) doesn't perform an optimization called tail call elimination that would make this program consume zero stack, which would make it hang instead of erroring out.
Some languages (like Scheme) are specified to optimize tail calls, so you can rely on this behaviour there.
