In vertical smokers if you set an extra drip pan over the factory pan, you can usually salvage the drippings. The temperature of the pan without water can reach the scorch-point of most drippings without evaporative cooling (water in the pan). If you don't use water in the factory pan, you may still eventually reach the scorch-point.
When I run with a wet-to-dry smoke chamber, if I want to catch & save the drippings in a secondary pan, I need to get them out not long after the water has evaporated from the water pan, or they will always become scorched at some point on longer smokes. If I run wet only, I can leave the drippings until the meat comes out. There are drawbacks to keeping the smoke chamber wet, especially if you want a well developed, hard bark on the meat, or a more bite-through/crisp skin on birds.
Eric