Just want to add on to what
@KnightDoc said.
Its not that its "wrong" to require you to withdraw from other schools when you commit to going to one, but it feels unjust because some students had to withdraw from their waitlists much earlier than other students, which kind of eliminates all "fairness" in the system. IIRC, I think Michigan State had a CTE date of like May 15th, or something. So if you were accepted at Michigan State but holding out for a waitlist acceptance from School Y and you were playing by the rules, you would have had to drop your waitlist at school Y by May 15th. Meanwhile someone else who's at Wisconsin-Milwaukee (CTE July 15th) and also on waitlist at school Y, would be able to stay on the waitlist much longer, thus giving them a better chance of acceptance (because more people would drop off the waitlist, if they follow the rules).
Its that sort of inequality if you will, that is frustrating people and makes them say "well, I'll just ignore my CTE."
Again, the rebuttal is "well life's not fair," and that's true for random events and things like that, but this was a system that AAMC created, meaning they created this 'unfairness' when there really was no reason to (especially because the old system [hindsight's 20/20] was working well).