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.