The Whims of a Fickle Manager.
The trouble is "we," the developers aren't the tech industry making the decisions. The managers, who once were full time developers, are making the decisions. I can say hey let's use this stable, mature tool, but which catches enthusiasm more? That or the guy drooling over React and all the complex mystery JS libs saying it's the best thing ever?
And/or the poor PHB falls prey to the sales pitch of "if you rewrite it in fad.js, you'll save tons of money".
Yup - unless The Tech Industry is going to come in and rewrite all our code into Flavor Of The Month (and do that every 3 months forever) I don’t really care what they “demand” - I’m too busy providing value for my customers to be shaving that yak
That attitude needs to get out of everyone's head. You are the tech industry. If you want to build something in Rails, a mature and capable framework that has tons of support and won't go away, just do it. Who's going to stop you? Applies to any other technology that's stable as well.