As a Rubyist it also seemed strange to me. As soon as Ruby 1.9 became stable, it was embraced by the community fairly quickly. Ruby 2.0 has only been out for a month and there are already projects that require 2.0. In contrast, Python 3 adoption still isn't finished, and Python 3 has been around for several years longer than Ruby 1.9.

I guess that the incompatible changes in Python 3 don't really help. Ruby 1.9 introduced incompatibilities but they were fairly minor and easy to resolve. The biggest incompatibility was probably the introduction of string encodings. Python 3 introduced a stricter string encoding system and changed syntax in some ways. Some of the syntax changes make it very difficult to write code that is compatible with 2.6, 2.7 and 3.0.