My guess is because they didn't qualified, not read the rules and follow the proper steps, or their accounts were deemed to be cheater or spammers. For example, in the current campaign that I'm in we have something like 5 or 7 thousands people who signed up, but out of that only say 500 to 900 have gotten anything. And it makes sense, because so many people don't follow the rules, or are a negative to the campaign because they are spammers.
Just look at the average quality of your bitcointalk poster, why would any coin want them to be part of their campaign?