Because UI is hard and people think they can come up with some framework to "fix it".
UI is inherently complex. The relationships between views, states, data and events blows up very quickly, and inevitably lead to code that gets messy. So people come up with frameworks to organize code and auto-generate some stuff. But then complexity doesn't really go away, so frameworks also get messy, and people come up with more frameworks.
Does it get easier overtime? Probably a little bit. But overall there is no silver bullet.
That said, the concepts are not different. Once you understand where the mess comes from and what the next framework is trying to "fix", things become a lot clearer, and you don't really have to learn much of anything to be able to use the newer stuff.
EDIT: also in javascript, it's very easy to roll out "frameworks". In other languages, UI libraries are deeply connected to the lower-levels of the operating systems. On the web, you just make a library that manipulates the DOM and CSSs, and everything else is done for you by the browser. It's much easier.
> also in javascript, it's very easy to roll out "frameworks"
Also worth mentioning that the switching costs for changing frameworks in JS is incredibly low. You can just load different JS files and presto - you can use a new framework. No servers to setup or anything like that
UI is inherently complex. The relationships between views, states, data and events blows up very quickly, and inevitably lead to code that gets messy. So people come up with frameworks to organize code and auto-generate some stuff. But then complexity doesn't really go away, so frameworks also get messy, and people come up with more frameworks.
Does it get easier overtime? Probably a little bit. But overall there is no silver bullet.
That said, the concepts are not different. Once you understand where the mess comes from and what the next framework is trying to "fix", things become a lot clearer, and you don't really have to learn much of anything to be able to use the newer stuff.
EDIT: also in javascript, it's very easy to roll out "frameworks". In other languages, UI libraries are deeply connected to the lower-levels of the operating systems. On the web, you just make a library that manipulates the DOM and CSSs, and everything else is done for you by the browser. It's much easier.