Nobody Cares About Signed Gems

Not surprised at all. The Ruby community is not very security conscious.

For example RVM install instruction used to be

  curl -L get.rvm.io | bash -s stable

(see https://web.archive.org/web/20120420030416/https://rvm.io// for proof), which is a recipe to get owned should anyone MITM you, poison your DNS, or rvm.io being taken control off).

At least RVM install instruction go changed to the safer (but still pretty vulnerable to an rvm.io compromission)

  \curl -sSL https://get.rvm.io | bash

But that the completely unchecked version lived for so long without anyone caring too much shows that the Ruby community doesn't care much...