And yet, in 99.5% of use-cases, it's infinitely more convenient not to have to jump through that hoop.

I've been a Ruby developer for… seven years now, and have literally never encountered actual problems in the real world by this, by mutable hash keys, or well over half the other issues on this list. And I'm willing to bet the vast majority of other developers haven't either.

Ruby has mostly sensible defaults that work as expected in most practical cases.