In deployment, we've gone from SFTP scripts to Fabric-like software to PaaS to configuration management software to Docker, and then it seems every 6 months there's a different preferred way to make Docker do something useful. And of course there's the eternal argument over whether to deploy to VPSes, cloud platforms, or bare-metal hardware.
The "hip" web companies at any given moment - the ones who need the latest and greatest components to impress investors and attract "rockstar" "10x" developers - aren't tied to any specific language. They'll pick whatever was the most popular at the time they needed to pick something. Hence, right now, you have a whole lot of companies building on Golang and node.js, where they'd've been building on RoR five years ago.
There's plenty more nonsense where that came from. That's just an easy to understand, concrete and obviously stupid example.
>Check out all the different server side frameworks and infrastructure components that have been in vogue with web developers over the last decade.
In python it's mainly been django and flask for a decade. In Ruby it's mainly been Rails.
Why do they have sticking power? It's partly cultural but it's largely because they were built on far more stable foundations.