There was also a lot of consternation when TCO was formalized as part of R*RS. It's a fundamental part of how Scheme works, so it was obviously necessary. But from a compiler writer point-of-view, it was a rather exotic demand at the time.

Though we've moved from a period of languages as defined by a spec to languages defined by implementation. Such as Perl, PHP, Ruby and Python. So what is "normal" has changed a lot.