It's notable that 1.9 came with a significant performance boost, so there was a good practical reason to want to upgrade. People were motivated by the prospect

It's notable that 1.9 came with a significant performance boost, so there was a good practical reason to want to upgrade. People were motivated by the prospect of their code running twice as fast - sure, the language was improved a bit too, but it's Ruby, it's already pretty nice, so that was hardly going to light a fire under anyone. When Python 3 turned up and it was on average slower, my first thought was "well, good luck getting people to adopt that".