You won't really encounter situations where you NEED to use those frameworks, but they increase your productivity when creating web applications. You should learn them so that you know when you should use them and when you shouldn't. Plus learning new frameworks (especially react) will teach you new ways to look at programming. Using redux (very popular addon to react) especially will teach you some pure functional programming. The idea of react (iirc) is to define semi-declaritively how your application should look for a specific state, instead of defining how your application should modify the dom when events happen which is what typically happens with jquery. On large applications handing state transitions becomes completely unmanageable, and react fixes that.
By the way, react isn't really a framework, it's a library which you need to plug with some other libraries and tools (redux, webpack, etc.) to make an application. I would suggest learning angular 2 at least, using typescript for some challenge and change if you're used to just using jquery.