I've only been attending for the last two years so I can't refute your claim that the problem increased when event tickets could be used as generics, but I don't think it is as simple as that. Compared to most peoples total gen con spending a two or four dollar event ticket is nothing. Especially since you paid for it seven months before the convention even started. I missed several events last year due to a family members flight in getting totally messed up by weather one day, and getting half way to Indy another (I commute the 60 miles from home) and realizing I didn't have my badge. So things happen, and none of those missed event tickets were used as generics.
This is what the ticket data supports, and to be clear - the rule hasn't actually changed. Tickets from other games have been accepted for at least 10 years. The only change was that not it's explicitly stated in the Event Host Policy, as opposed to some GMs knowing about it and others not.
There has been no significant increase in either no-show rates or rates of tickets being used for other events since that was made more clear.
The net result of the rule is that more people play more games because they have the tickets to do so. And - presumably - any spots they never show up for can be filled with generics.
The alternative would be for GMs to have to tell more people they can't play because they don't have the right ticket, and it would significantly complicate many TCG (and other tightly-scheduled) tabletop programs.
This all matches up with my own anecdotal experience: players skip out on events because something comes up. They see friends, get dinner, get distracted, get tired, etc. Those things are still going to come up and they're still going to flake out. Losing $4 is going to stop them, it's just going to sour their experience a bit and maybe stop them from playing something else.
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