"Unless it's done right" is what they always say, and I guess by your book "they" never do it "right". :\
I realize I'm coming off as uncharacteristically antagonistic in this thread and I'm not intending to, but I've seen this discussion flare up on several franchises with pending (or potentially pending) treatments. It's never what is wanted, but it usually ends up selling more than amply to justify the development.
Plus this is a terrific way to get people heading into a new console generation aware of a brand name with more big plans. That's the biggest reason for it, I think. But it's never about spending a great deal of money, it's supposed to be a shorter-term investment and frankly doing the gameplay things people always wish for would dictate something roughly on-par with a medium-scale new game in development costs.