Perhaps DL and UA website developers go back and forth between the two, dragging both airlines' websites lower together. Compare this with the fantastic functionality of some foreign carriers, you have to wonder to what extent DL sees advantages to it's worst-in-class website.

For quite a while DL's interface showed steady improvement (well not always steady). It now seems to have peaked and is on the way down. It's pretty clear they are working on it, since I've had the experience this past week of getting frustrated with the new "features" and stopped looking for flights only to return the next day and find the older interface. If would be nice if each time they throw the new version at us, they were counting on us, through this group, to tell them what does't work. But then we've been telling them about the problems with the DL website for years; they haven't usually been responsive.