Considering mobile is such a large portion of the Web right now, and likely to become even larger, yes, a shame indeed.
When WotC designed DDI, and then re-released it, mobile gaming was a very, very small portion of the population, and no-one (except perhaps Apple) thought that it would take off the way that it did.
Also, to respond to an earlier poster, when DDI was first designed, Windows 7 was just in the beta stage. Expecting WotC to be able to successfully predict what MS was going to do with Windows 8 is, to be blunt, unrealistic.