Clearly, it's to keep you screwed with bad credit. Once upon a time, I was blocking the numbers of CAs left and right. Now, they avoid me like the plague. Unbelievable! My phone never rings after finding this forum and sending out PFDs.
For once in my life, I have the funds to rid myself of nuisance accounts. But no one is taking the bait! I'll check my PO Box tomorrow in hopes of a response to my offers.
I must learn patience. 
Starting Score: FICO TU 591 FICO EX 581 FICO EQ 555
Patience is a good thing. If they don't respond to the PFDs, send them again.
July 2013 score: EQ FICO 819, TU08 778, EX "806 lender pull 07/26/2013
Goal Score: All Scores 760+, Newest goal 800+
Take the myFICO Fitness Challenge
Current scores after adding $81K in CLs and 2 new cars since July 2013
EQ:809 TU 777 EX 790 Now it's just garden time!
June 2017 update: All scores over 820, just pure gardening now.
Thanks again, myfico friend. The new FHA guidelines re baddies freaked me out! I have time on my side but need to grow patience. A mortgage is the ultimate goal for this time next year or so...I need the collections gone gone gone...
Quite possibly...However, they are known to delete for whomever they choose to delete for. I think it depends on how they feel that day and how much you offer.
RobertEG suggested in previous posts -- "that a PFD is requesting two concessions", if you don't offer to PIF. I also believe this is true. There's also a human element that I think complicates the matter. The CAs are also aware that deleting is only advantageous to YOU! So, why would they care to assist. Merely, paying the debt won't help as much as a complete deletion. I think they are getting hip to the game.