I have been doing sales and marketing for the home video studios for many years now, and trust me when I say the studios welcome the stupidity of the average consumer.
The most amazing thing to me, is when the consumer KNOWS that a new or special edition is coming out, and they still purchase it twice. Dogma and the Lord of the Rings are two glaring examples that come to mind. In Canada, LotR is released by Universal Studios (they distribute New Line up here), and they actually did a consumer marketing campaign that explained that only 90 days later the extended version would be available. I would guess that a good 25% of the people who bought the millions of copies of the extended edition already owned the regular version...
And don't even get me started on what Anchor Bay has done with the Evil Dead series - each time having it outsell the previous. Insane...