This. Side by side windows and horizontal splits make it so vertical tabs are not that useful.

TBH in general I find tabs less useful as they multiply. Most of the time I just Cmd+A in chrome to search for the tab I need.

Not to mention that many Web sites are not optimized for modern screens, let alone truly large ones. There are still far too many absurdly narrow vertical text columns, riddled with tiny non-expandable images, on sites that appear to cater to 640 x 480 screens of yore.