I have 1Password vaults in 3 different shared folders in addition to the default 1Password app folder. I use these shared folders to share vaults and passwords with my husband, my sister, and my parents. When I update our bank password, for example, I don't have to update it twice. It is stored in the vault that my husband and I share. This is critical to my use of 1Password.
I would much rather have this scenario (and give 1Password access to my full Dropbox) vs having all of my data on AgileBits servers and paying for an account for families or yearly for each individual. If 1Password went to requiring vaults to be in a specific, app-permissed folder, it would break my workflows completely.