Then why do it?
You just said yourself:
I bought Big Hero 6 on blu-ray, a couple of weeks ago. A Disney title. But, what's this? Oh, they've decided to re-release their titles with stupid fucknut numbers on them now. Why? So's we'll go and buy them all now, otherwise our collections will look odd. Now, of course I'm not going to buy all of the other Disney titles but some people will, including purchasing titles they wouldn't have done for any other reason than completist purposes. Keen collectors of the Wild East movies have definitely got at least a few titles they wouldnt have purchased outside of that completist compulsion to "catch 'em all!", like Pokemon. If you've been collecting the Wild East spags up to now, you're going to have to get number 58 irrespective of what it turns out to be. That, is sales based on a marketing ploy rather than the product itself. It won't matter what the product is.
And in the meantime, I've got a film with f*cking "Disney Classics 53" written on it for no poxy reason.
Well, they wouldn't want to make money off of crappy films by way of numbering them so obsessive compulsives have to buy them if they're doing it for love, would they?
They're not charity cases. You're advocating that the "advantage" they take us of their customers. And bilking the public oughtn't be their preferred method for earning money out of them.
I'm not getting at the folk who end up forking out for these things; that's up to them. I've done it myself enough times, buying sequels I don't care for because they link up sequels I DO care for. But let's not pretend that arbitrarily numbering an otherwise disparate bunch of movies is anything other than a tactic intended to get people to buy something they mightn't have done otherwise. Wild East could still have called their spag collection "The Spaghetti Western Collection" without the numbers. And let's certainly not suggest it's okay to use such tawdry tactics just because a company might be a small company who needs some money.