You have just never done a responsive design. Inline styles can't be overridden on screen size and having all the styles hidden behind a random class name makes

You have just never done a responsive design. Inline styles can't be overridden on screen size and having all the styles hidden behind a random class name makes it hard to figure out what's being specified but if class names tell what styles are applied, you don't have to go edit part of a css just to change margin size.