Why does bootstrap use these bracketpoints?

Question

Bootstrap

Greetings.
As you know, bootstrap has such breakpoints:

xs: 0,
sm: 576px,
md: 768px,
lg: 992px,
xl: 1200px

The main container has the following dimensions:

sm: 540px,
md: 720px,
lg: 960px,
xl: 1140px

What caused the use of precisely such resolutions and sizes? let's say why 1200/1140 and not 1280/1200. block size 960 - there is such permission, but the break point is 992 and there is no such permission. If my question seems stupid to anyone, please don’t throw hats) The
Foundation, for example, has the following:

small: 0px,
  medium: 640px,
  large: 1024px,
  xlarge: 1200px,
  xxlarge: 1440px,

Answer 1

in short - BECAUSE