If you’re adding ‘content’ directly into a div that has some utility classes for a grid system, like Bootstrap or Foundation. You’re tying that content to that grid.
The idea is to abstract the grid from the content, a separation of concerns, so that it’d make it more portable if needed. Jeet get’s rid of the need for the grid div elements as it’s in the CSS (Sass) which I’d suggest is a lot easier to edit than picking through various divs with grid classes added to it for responsive web design.
Obviously there are two trains of thought here in regards to using a grid system within your markup or within your CSS. I, personally, prefer to add it to the CSS, like Jeet does.