Just now I was trying to look for games like Destiny 2 that were less grindy/not live service, and I realised that after looking through a lot of the "Looter Shooter" tag, a significant portion of the games were Roguelites. This is one example, but there are plenty of other times in which this would be useful - if I wanted to look for queer centric games without being bombarded with futa porn, for instance. This is why the ability to exclude certain tags would be incredibly useful for searching for games.