Scenarios are different. In some cases, customers didn't wish prvode connectivity to Internet, only LAN connectivity...
And i think, ability to configure manual wan static ip will be very cool. Because if i will config AP in one location via internet with static settings, then move it to new location, there can be case that i have mistake in typing some values. So, AP didn't start and i can't check anything. I loose few hours with trying change cables, resarting, waiting long boots and... nothing! Then I will need back to 1st location, reset AP to defaults, because with manual ip settings for wan parameters for another place AP didn't connected to Internet and i can't recheck it.
If imagine that i can change this setting locally, may be via LAN port only and change it, it will be greatly easier and time value deal. As example my 11D didn't have mormal lan status led's for wan port and i can't check simple thing - is there link up or down.