Frameworks in software provide new methods and tools for different projects. In my case of UI, different UI frameworks provide different ways of designing and implementing features and looks across sites. In that way, a framework is basically the base of whatever it is you are doing, because presumably if you are a specific framework, you are using it with the intention of taking advantage of its features that maybe vanilla code or other frameworks do not have.
As previously mentioned, some frameworks offer different features or more streamlined ways to obtain desired looks. However, these frameworks themselves can be quite complex on their own, and figuring out how these new features and implementations work can be a hourslong task on its own.
That said, the number one reason I have to use UI frameworks is formatting. Which, if you are a smartass, seems to be the same thing as design. However, really what I mean is the process in which you format. At the end of the day, with enough work and time you could probably implement the features of some of these frameworks yourself. But why do that when you can have something do it automatically for you? Now we don’t need to worry about pixel-perfect placements since the framework will handle it for us.
Furthermore, the modern age has brought a multitude of devices with varying screen sizes. 6 inch phones, 9 inch tablets, 15 inch laptops, etc. mean that your sites might have to be adaptable. Frameworks like Bootstrap provide means to automatically adjust UI based on screen size. So now we don’t need to worry about making 4 different versions of our site. Just one with the correct parameters, and thereby we only need to keep track of one master site.
That wasn’t too long so hopefully you made it here. Thats all I really had to say. Thanks.