I agree Pete, well sort of...
I'm a fairly young guy to be writing this stuff at 30. I got turned on to ambient music about 5 years ago. I think ambient often appeals to those who find the pace of life to be a little too speedy and chaotic. Depending on ones experiences and situation, you can reach this point young like myself, or 60, or anywhere in between. By the time I was 25 I was already feeling like life was slipping by just a little too quickly, and the pace of everything just too intense. Ambient filled a need in my life in that it forced me to sit down, relax, and just open up my mind to the music, and not think of the previous day and it's happenings.
I think most people in the western world reach that point at some time in their life, it just depends when.
When I look at the cross section on my own Last.FM page, it's all over the map, from 17 year olds to geriatrics.