Why? In all CSS frameworks (bootstrap and so on) you find a container (Why? DRY - don’t repeat yourself). If you want to use a regular div (Container are not semantic tag or html5 tag - only acceptable
class name).
Another reason - On webflow it’s easier to recognize the container (Another icon) under site tree (More organize project). Last on a team, it’s better all members use the same ideas (And not each time another developer use another idea for basic container trick - max-width and margin-left/right auto).
Also usefull - how to change webflow container width: