I would guess a combination of tech evolution, legacy code and disagreements between design departments. I once worked at a gamedev company that had an in-house

I would guess a combination of tech evolution, legacy code and disagreements between design departments. I once worked at a gamedev company that had an in-house scripting system and a purchased system from an engine fire-sale (not a fire-engine sale). The in-house one was better for complicated situations, but was relatively a lot of work for large volumes of simple situations.