I don't think that's entirely accurate. Lots of Rails users went the SPA route the second stuff like Backbone came out. Wycats was big in the Rails community at this time and he spearheaded Emberjs. The Shopify guys were (and are still) big in the Rails community and they created their own Batman.js. It's just that the Rails core devs made a decision to not go that route. They were even working on their own front end framework at one point and after some time they decided to kill it in favor of just using pjax/turbolinks. You can get your 80% case accomplished with these technologies with substantially less effort. There are definitely reasons to go SPA, but the dev community at large has jumped on the hype train here without really identifying that using these technologies are a good idea for their use case. I mean, there's a lot of people doing CRUD with React. That's crazy.