Have you ever worked a new, somewhat elusive or rare grid, only to find that the station you worked does not QSL in any manner whatsoever: no LoTW, no eQSL, no paper QSL. Any there is no email address to even communicate with him/her?
About 1 percent of all new grids/prefixes fall into the category of "no confirmation likely". One saving grace to all of this is that folks who once were "Zero QSLers" convert and upload their logs to one of the QSL services recognized by GAPAwards. This happened recently to me with a Russian in an elusive grid that I happened to work in 2014. When I did my daily download of LoTW confirmations there he was!! Two years ago a similar incident took place: a QSO from 2002 with Indonesia confirmed via LoTW for a new grid.
That's why I talk up LoTW and eQSL primarily, as well as ClubLog (seems popular with Europeans and some Japanese) and even HRD. LoTW, ClubLog, HRD and others are free - eQSL is a dollar a month.
You can maximize your grid/prefix count by subscribing to multiple QSL services. Check with Ernie if you have questions on exactly what a "GAPA confirmation" is.
GL, 73, Rich, K3VAT