what's the use of these tags?
(say, compared to an AADV tag)

i have a few dozens collected over different FFPs, different tiers with the same FFP, and for different years within the same tier of the same FFP.

to me it is only useful if you want to make sure the piece gets back to you and do not want to release your contact info.
(well, other than showing off you are a top tier FFP )