Gather round, ye young players, and let me tell you stories of old. In the before time, The Games Workshop magazine, White Dwarf, came with a listing of all of the possible pewter bitz in the ENTIRE GAMES WORKSHOP LINE. You could call GW and order any bitz in any quantity or combination. I used it often, as there were some things that I needed that you just couldn't get in the blister without a huge amount of waste.
For example, back before plastic Assault Terminators, I needed a Terminator Sergeant with a Thunder Hammer and Storm Shield. The only sergeant model sold in blister had a power weapon/storm bolter. So, I bitz ordered a Terminator Sergeant body, a banner pole, and a regular Thunder Hammer/Storm Shield arm combo. Bitz ordering gave me what the blisters could not.
There was another, even SWEETER side to this. If you attended Games Day, you could buy ANY pewter bitz BY THE POUND. Want 20 meltaguns? Sure. Would you like 80 copies of the Eversor Assassin backpack? NO ONE CAN SAY NO TO THAT. It gave a DAMN good reason to attend Games Day, and let me make a HUGE amount of conversions in my army today that I would never have been able to do.
GW never intended to do individual plastic bitz and I understand that. The internet market has stepped in and filled that void. But it is incredibly rare to find any pewter bitz on non-GW ordering sites. There are a couple but they don't have the entire range.
Sure, as more plastic kits come out, pewter is becoming obsolete. But there are some times when you just need that old archive bit. My buddy Lexington loves the old fan-style Space Marine Jump Pack. Having the old archive bitz gave modelers the ability to make anything, without having to track down old stuff on ebay.
The bottom line is that there are old pewter bitz that I wish everyone had access to. GW does give some "upgrade packets" prices, but you have to buy the whole thing. What if you want an odd number of shields?
I get why they stopped. It costs money to hire dudes who will paw through the archive and get the bitz people like. Charge us a handling fee! I'll pay it if I need the bitz for the perfect conversion! WE ALL WILL! WE ARE ADDICTED.