Lego knows that their customer base includes adults. Besides expositions and clubs that get some support from the company, you sometimes see Lego sets with a photo on the front of the box featuring an adult male instead of little kids!
Another thing I've noticed about Legos since rediscovering them a few years back: They have a really sophisticated retail operation that's not unlike what Apple does with the Apple Store. They're well designed, have very knowledgeable staff, and feature lots of goodies that you won't see in mass market retail outlets, including high-end sets and even a 3D animation/"augmented reality" that is activated when you hold certain boxes in front of an in-store camera (see http://news.cnet.com/8301-17938_105-20003273-1.html)