That part may be true for some but when we bought in many years ago, and understood that the perks may disappear, we bought anyway because of the huge savings on rooms. Our guide was very adamant on that point. He wanted us to be sure that we are buying in for the right reasons.But a perk is an advantage/benefit by definition. If those so-called "perks" disappear, there won't be as big of an advantage or benefit for joining DVC, therefore there will be less incentive to join.
We are discussing EMH, and since there are only a few thousand DVC rooms compared to regular rooms, it will affect regular customers a lot more. As a matter of fact, we AVOID EMH. We are older, so don't stay out at the parks until 3am. Yes, we do go early, but only to the park that does NOT have EMH. The park that has morning EMH gets a lot more crowded a lot quicker after the regular visitors start poring in. We have learned to avoid them, since they provide very little advantage, since it is only an hour.