I really like the contrast of ease of use vs ease of learning. However, I don't think designing an interface that is good for both is fundamentally difficult.

I really like the contrast of ease of use vs ease of learning. However, I don't think designing an interface that is good for both is fundamentally difficult. The problem comes from evolution. In early versions, with only a few features, none of this requires a ton of thought. As features are added, it's rare that an overall UX re-design is undertaken, for a few reasons. For one, the people working on it and using it day to day are incrementally learning changes, and have time to adjust. In some cases they probably don't even notice the UX learning curve problem as it takes time to become apparent. For two, existing and power users will freak out if a new release changes shortcut keys or otherwise "moves the cheese". Think of the outrage if vim were to announce "we're changing all the commands to be fully consistent with each other, but it means every command you've spent years memorizing is now incorrect. Even for the most UX-focused team it's impossible to predict the feature set a product will have in 1, 2, or 5 years, so of course by the time you get there, the UX has issues.