A few years back, a designer blogged about a similar redesign for American Airlines. He was contacted by one of AA's in-house designers, who wrote about the internal politics and hurdles that get in the way of changing things. AA later sacked the designer for violating his NDA and the articles were deleted from the blog, but the entire episode was pretty interesting. If you're interested:
Copies of the Dustin Curtis & Mr. X posts http://www.flipthefunnelnow.com/dustin-curtis-%E2%80%93-dear...
Aftermath http://www.techdirt.com/articles/20091106/0337536829.shtml
Even if a redesign doesn't touch any of the regulatory verbage and requirements, it still has to go through largely the same pipeline of internal approval as if it did. So even minor changes are viewed the same as significant ones.
Take the boarding pass. Given the limited amount of information present, redesigning them for a better experience should be a fucking no-brainer. No matter how long you search, I doubt you'll find anyone genuinely satisfied with their boarding pass. They're big, ugly, and reasonably unclear at a glance. You see tons of redesign experiments online, but no airline ever seems to take the hint or be inspired by them. Here's a semi-recent one that I love:
http://petesmart.co.uk/rethink-the-airline-boarding-pass/
Beautiful typography, perfectly sized for your passport, and easy to read at a glance. Throw in the time difference and predicted weather for your destination, and the redesign is utterly perfect. What's not to love? And yet, nothing.
I see two big problems with the status quo in that regard: first, you the almost reactionary mindsets that seem to become not only more common, but also even more reactionary, as a company grows. Self-deceptive thoughts like "change is scary/costly/will scare away all the customers" are pretty damned powerful. Along with a lack of genuine demand for the change in the first place: bad UI hurts customers and drives away sales, but quantifying it directly in a way that makes it a priority in itself is difficult. They're all the more powerful by the fact that they originally stem from genuine concerns. And these attitudes are practically everywhere. Hell, even apple.com took the better part of a decade to see a significant shift in its UI + design:
http://mac.appstorm.net/roundups/graphics-roundups/the-evolu...
It's really no wonder nothing changes. Until we start to see shifts in those attitudes, we're going to be largely stuck with the same bad UX in far too many places. :(