AARP continuously sends mailings to me without much reason other than past agreement-upon-demand during a demand-strategy telephone contact that retired people who want to organize such a membership should be free to do so. (Because the same call-demand telephone networking operation has a significant death rate, however, network participants must be reported to police and/or FBI with predictable frequency; indeed, those formally designated 'retired' might well have become more categorable in terms of questionable paramedic visits and movements oversight.)
I am not a retired employee nor usual company-retiree-aged and do suspect that lack of spell-out for 'AARP' acronymn within by-mail literature and Internet website means yet another organization initiated upon demand without much discussion or debate, such that the 'American Association of Retired Persons' might eventually go the same route as the former 'National Organization of Women', which became quite suddenly the 'National Organization for Women' as the result from a paperwork change.
Pages of fine-quality paper stock are received in the mailbox throughout past years continuing to the present time, naming me as a potential member. The most recent mailing includes a return envelope with detachable 'free-gift' notice, and a legal-sized perforated form holding two plastic membership cards (one for me and one for other household member).
So, what say? 'of' or 'for'? That younger, non-retirees are being "welcome"ed to AARP means that the organization might be overcrowded with 'special' interests that might exploit retirees who really need help -- help needed perhaps because claimed by the same 'special' interests against which AARP was formed to protect. This isn't a self-concept but rather an acknowledgement that retirees hold caches of lifetime memories and experiences which AARP can serve to enable those to contract with interested biographers or memoirwriters without the direct elbow-rubbing contact that non-retiree AARP members bring to the organization (including drag that routes retirees into more work roles as action that must be energetically protested or...).