Why do we need frameworks, actually?

Question

I've heard lots of frameworks like Django, Flask, Ruby on rails, Bootstrap...But why do we need them?

Answer 1

They are just tools. They are only supposed to make programming easier.

One of the real world reasons to use them is that some companies would propably use a framework and require their participants to have basic understanding in it.

Answer 2

Because for example Django is entirely written in Python, you would not in theory need Django for anything, because you could perform all it's actions with Python code, but because Django is very optimized in web backend development with Python, it would help Python developers a lot to develop backend parts of websites.