And it still is - the efforts people still go to to produce Counter-Strike maps, working around the quirks of the various game entities that don't properly reset at the end of a round and so on.
In many cases, specifically working with those kinds of quirks. Being able to persist certain state between rounds in CS using these kinds of bugs has been a godsend for many custom game modes (for me personally, my work with Zombie Escape in CS:S and CS:GO)
