I don't think that's entirely true, they allow for building experiences that weren't really possible with the previous model of rendering entire pages server side on every action but they aren't easier in all respect to that. If you site is mostly static data, it's probably still easier to use the older model. SPA frameworks start to make more sense when you want to build interactive pages with components that you want to individually update etc...
But they do add complexity that can't be ignored. that's why tooling and frameworks are hugely important as they smooth out that complexity.
The biggest "easier to develop" thing for me is the ability to have the SPA separate from the server. Being able to deploy beta builds, one-off builds, etc makes it MUCH easier to diagnose production problems.
So, I guess I'm saying that it allows for much shorter iteration times, ability to experiment with solutions in the production environment without requiring complicated server solutions.
Granted, that also lets me build experiences that weren't possible, because I can experiment more and have a faster feedback loop, but for me, it's because I can DEV better.
I don't think that's entirely true, they allow for building experiences that weren't really possible with the previous model of rendering entire pages server side on every action but they aren't easier in all respect to that. If you site is mostly static data, it's probably still easier to use the older model. SPA frameworks start to make more sense when you want to build interactive pages with components that you want to individually update etc...
But they do add complexity that can't be ignored. that's why tooling and frameworks are hugely important as they smooth out that complexity.