I've always thought this was an incredibly stupid marketing ploy, even more so in this day and age of the internet. Disney is practically encouraging people to illegally download their movies.
The vault works the other way, too. It's keeping people from buying their products that HAVEN'T been released yet. I've been waiting for Aladdin on Blu-Ray (it is my favorite Disney animated feature), but it's been stuck in the vault. It was supposed to get released this year, but was cancelled. There's a region-free version on Amazon, but it's got no bonus features, and I'm not sure if it's been remastered.
Sure, I could download a low quality rip, but I would prefer to have the highest quality transfer there is, as well as the Diamond Edition keepcase.