Is Bootstrap necessary other than for markup?

Question

Bootstrap

Hello.
I have my own little grid framework, which is enough for me. It's also built on floats, not the new flex. I've been playing with Bootstrap for a couple of days and I don't understand why it is needed, except for markup? It makes no sense at all to use its standard elements and styles, each site is individual and all this will have to be redone anyway.
So why then bootstrap with all its add-ons? Is it often used with all its elements or just rip out bootstrap-grid and use it?

Answer 1

Why is Bootstrap needed?
Why use bootstrap for PSD design?
Why do we need css frameworks and why is there so much noise around "grids"?
How do you feel about Bootstrap 4? And do you use it in your work?
What do you use most in Bootstrap and do you use it at all?