It seems self-evident to me that WotC is concerned about those who didn't convert to 4e. Like it or not, the launch of 4e did alienate lots of D&D players, and the success of Pathfinder shows that those folks have moved on. One rule of business is to keep your existing customer base - that ought to be a lot easier than breaking into a new demographic/area. And 4e was not nearly as successful at that as 3e. (I have no idea of the relative success of 4e and Pathfinder, except to say that both are obviously successful.)
If you don't believe the logic, look at Essentials. The original strategy was for this line to draw in new players. (The original strategy for the main line was to make existing customers happy - obviously that had mixed success.) Now, with specialty classes and variable power structures and auto-hit magic missile, Essentials is also trying to bring back the "old school" feel. Presumably that's to appeal to customers they have lost - because obviously the current 4e players don't care much. So, evidently, WotC wants to appeal to their lost customer base. If they believe they should do so, why shouldn't we?
Also: hooking them young in order to maintain a long-term revenue stream only works if you can keep them hooked. To the extent that older gamers drop out of the system because the company focuses on the next generation, it's not going to work.
On another topic, of course pre-3e pdfs weren't a big moneymaker. But that's not the point: WotC yanked them from the shelf and alienated even more people. It takes almost no effort for them to be there - since all of that legwork had been done years ago - and, really, does anybody honestly believe that 1e adventures compete with 4e? Fans of those editions have an absolute right to be angry at WotC over yanking the products they like, as I'm sure many 4e fans would be angry if they quit supporting that game.
The reality is that older edition pdfs were a casualty over concerns about piracy of 4e books, and I believe an unnecessary (and unfortunate) one. No doubt the profits were small, so they didn't bother distinguishing them. I have no illusions that DDI should include support for past editions, but I think that making pdfs available is such a trivial thing, and would generate such goodwill, that they ought to do it.