Open-but-backlogged is OK!
I'm sorry for using such harsh words; I was flabbergasted and lost my calm. As for why, there's so many reasons that it's hard to find where to start, without launching into a thousand word essay.
- Usually closed means either this has been done or else we've thought about this and decided it doesn't need doing; closing a ticket just because it's old adds noise to that signal, especially when you can already filter by date.
- Creating new tickets that are duplicates of closed tickets also adds noise, time and confusion when searching for those issues, and for people who were monitoring those tickets, and can make the status of the work unclear to people other than yourself.
- Tickets are valuable documentation; duplicating tickets is duplicating work.
- There are many possible reasons why someone isn't hounding you every six months about an old ticket, which aren't all "it doesn't matter anymore". Maybe it's not their personality to do so. Maybe it's because they thought they already did what was necessary: create the ticket and leave it in capable hands. Maybe it's because they got frustrated and switched to a different product.
- Priorities shift over time, but not always in a direction of older --> lower priority. Sometimes everything gets swept off the table to fight a fire, but once the fire is out, the old stuff becomes high priority again. Sometimes a blocking issue needs to get resolved first, and that can take time. Sometimes a ticket requires a lot of resources that only become available down the road.
Etc!