There are leftover tags because they are either tags no one wants for good reasons or they are tags that people drew and never paid for or returned.
The secondary draw and leftover list is partly due to the fact that Colorado doesn’t make you pay up front so you get a ton of guys that put in for tags in multiple states and then pick and chose which ones they want after the fact.
The whole leftover list and secondary draw wouldn’t have to be a thing if they had a system where they just went to the next person in line that applied for that tag when they have a non-payer or someone return a tag.