Let's also remember that a lot of these retired greats are probably more cost effective to include in products. Most of these guys rely on money from autograph signings to get by because they didn't make nearly as much money as players do today, and they sign a LOT. They can get these players to sign for a fraction of the price of a current star.
Take one look at a site like Frozen Pond for an example: A Bill Ranford signed 8x10 goes for $39. I'll use Ranford as an example because he was mentioned above. A few examples of recent stars, sticking with goalies just for comparison:
Johnathan Quick: $89
M.A Fleury: $75
Martin Brodeur: $125
Roberto Luongo: $125
Antti Niemi: $79
As these are retail prices you can assume that a card company would get a much lower price for bulk autographs, so let's take a guess and say that Ranford signs for around $5-$10 a signature, which is probably still being generous, while a guy like Brodeur might sign for around $45 or higher. If you're in charge of building an autograph set with a mix of players new and old of course you're going to include guys like Ranford if you can get them to sign. If the entire checklist was made up of superstars charging a fortune for signatures the product would be too expensive.
The secondary market may not be kind to some of these players and collectors who are after the latest and greatest may shake their head but guys like Ranford are not only worthy of some hobby love but also financially necessary to help balance out some of the rising costs of producing a set to keep us happy. We all want the big name signatures but we don't want to pay big name prices for packs so that's our alternative.
Other factors probably come into play like the players' willingness to sign a deal, how well he is accepted by the hobby, whether or not there is game-worn material available to use, how well he was treated by card companies in the past, etc. I know Dryden doesn't like people making money off his signature and he's also in politics so I guess he decides to handle himself a certain way so that's not the fault of the card companies.
All retired players have to have deals in place before a card company can use their image and signatures so it's probably a nightmare trying to wrangle in some of these guys to include in your sets when everybody wants things done a certain way or whatever. Remember a short time ago when Vladislav Tretiak ITG cards had an extra disclaimer on the back about the memorabilia not being guaranteed by Tretiak? There's probably countless little quirks that go into these deals that we never hear about but give the card companies headaches and that could factor in as well.