The vast majority of websites out there use a grid. They may not explicitly have a grid system in place, but if they have a "main content area" floated to the left a "sidebar" floated to the right, it's a simple grid.
If a more complex layout presents itself, people often reach for a grid framework. They assume grids are these super difficult things best left to super CSS nerds. That idea is perpetuated by the fact that a lot of the grid systems they reach for are very complicated.