1. Thats pretty much all airlines (can/do) differentiate on. The mainframes running pretty much all the ticket/seat allocation worldwide are sooo old they only handle pricing. And no-one can fix them because everyone plugs into it.
2. Actually thats all we really do care about.
(2, is less true. I am going to be taking my kids on a long flight soon. I would pay extra for an on board creche / nanny. But there is no way of putting that flag on any flight search so no point in offering it.)
This is a perfect example of how technology encourages a flight to the bottom. You have US air. Why? Maybe they only use lemon scented paper napkins. You would like to search for flights that never use lemon scented paper napkins, but you cannot, so there is no way to tell if spending 100 dollars more will make you happy so why bother?
And maybe its only worth 50 dollars to you not to get lemon scented ...