Nope. Ubuntu and Debian are not at fault. They have to pick a version of Ruby which runs the user applications that Ubuntu and Debian package, which will be kept working throughout the support period of the OS release. Everything else is secondary. They don't get to upgrade versions half-way through the release cycle, either.
This is why it's not realistic to expect to use the system ruby for development: that's not what it's there for.
It's also worth noting that the version of Ruby in current Debian Stable (which is 1.9.3-p194) will in all likelihood be deprecated by ruby-core 2 years before the next Debian Stable release. Again, this is fine for Debian, because they have taken on the responsibility of keeping working the user applications which rely on the system ruby.
If you're complaining about the system ruby being so out of date that you can't develop applications on it, you're doing it wrong. The system ruby isn't for you.
This is why it's not realistic to expect to use the system ruby for development: that's not what it's there for.
It's also worth noting that the version of Ruby in current Debian Stable (which is 1.9.3-p194) will in all likelihood be deprecated by ruby-core 2 years before the next Debian Stable release. Again, this is fine for Debian, because they have taken on the responsibility of keeping working the user applications which rely on the system ruby.
If you're complaining about the system ruby being so out of date that you can't develop applications on it, you're doing it wrong. The system ruby isn't for you.