Based on personal experience, of course...
1. Someone you like/love gave it to you
2. You remember where you bought it
3. You remember why you bought it
4. Something momentous happened while you were wearing it
5. You'd forgotten you owned it until you unearthed it
6. You don't want to be wasteful
7. You plan to get it fixed/mended/adjusted
8. You want it but don't have space for it
9. You plan to read/where/use/write about it...someday
10. You can't figure out what else to do with it
