Video used as textures, either in world on 3D meshes, or as part of UI (HUD) elements. It could be prohibitively expensive to play a single video in some scenes, and we didn't support multiple videos. Not because it wasn't possible or anything, mostly because performance, although there would have been an engineering cost to doing also (ie I would have had to add support to the engine)
Also remember "expensive" is relative. I think it added little over 1ms to total frame time per video, but in a 60fps console game that. Our budget was about 1ms or less for the entire UI during gameplay (including scripting, layout and rendering), so a video could more than double that. 4 simultaneous videos would be like 1/4 of the entire frame :).
