I guess adult fans entering the stadium using a child's, or concessionary pass, is a nigh on impossible task for the stewards to police on the day, especially with all passes looking identical.
Maybe in order to make the job easier, adult passes could be one colour, and child/concessionary...
Well yes, precisely this really. For some people, human nature being what it is, if they don't get what they want, it's always going to be the other persons fault, regardless of the circumstances.
On your second paragraph, yes I agree too, It wasn't so many years ago that a season ticket was totally non transferable. It had to be used by the person it was bought for. End of.