I agree with your last comment, Greg.
I would guess that Adobe get a lot of Photoshop users to try Lightroom (and often in combination with PS).
Apple has all these nice free amateur programs - GarageBand, iMovie, iPhoto – that come with the computers. And then they offer the excellent pro versions: Logic Studio, Final Cut, and now Aperture.
First people may discover the iPod or iPhone, then the computers, and with the computers the free software. And from there, if they like iPhoto, and photography, they may be tempted to buy Aperture. (And after using Aperture for a couple of weeks, they realize that they need a better Mac, because everything is so slow...etc.etc)
The point is that the potential customers of Apple and Adobe come from different places.
Since Logic and Final Cut are among the best audio and video editing programs on the marked, Apple has to stay on top with Aperture too. But that argument applies to Adobe as well.
I use Aperture, and I have two serious problems with it.
1) They don`t update as often as Lightroom when new cameras are released (and not as many cameras, which is a problem for me, using the Ricoh GR-D as well as a Canon DSLR).
2) Ideally you need the best Apple computers to use Aperture efficiently. And that makes it a much, much more expensive program than Lightroom!
One problem for Adobe, is that their new customers may become confused, when they try to choose between Photoshop, Photoshop Elements, and Lightroom.
You have to understand something about the principal differences between Photoshop and Lightroom, before you know what to choose.
For Apple this is not a problem: you don`t need to understand much; you may as well misunderstand, or just think that one of them is "amateur" and the other one is "pro" – and go from there.
I can`t see any other solution for Adobe, than to offer Elements only to people who buy other Adobe products. Let´s say that Lightroom buyers get Elements for free (or, say, for 30 US$), as a way to tempt them to buy the expensive program as a supplement to Lightroom.
In any case, both Aperture and Lightroom (which I used a lot in beta) are great programs, and I hope the competition over time will only make them better.