I'm in the same camp. I know everyone is gung-ho on separation of the presentation layer, but I believe styles are far too intertwined into the presentation for semantic markup to be beneficial at a large scale. My primary concerns with semantic markup is that there's no quick way in your developer tools / inspector to lookup correlated rules in your LESS/SASS files and have them make sense (i.e. how many columns is this and how does it handle responsively?). As @bguthrie said, there's little you can deduce regarding relationships between the CSS file and the HTML markup. For this reason I stick with classes, as it's far easier to tell how my layout/grid is structured by simply viewing the source. I'm sure many will opinionatedly differ, but it's worked just fine for me for a decade and I find it easier to maintain and for other's to understand the structure on first glance of the HTML.