Why don't more people build their own custom computers, slap gigantic heatsinks on the processors, and then tweak the bios settings to make the processor run 1000Mhz faster than it is rated for? You can you know!
Why don't more people enjoy fine wine, or jazz or classical music?
You've asked a question that is almost impossible to answer, but I would speculate as follows.
I. High-information costs
The costs of acquiring, processing, and using information related to component selection are high. It is easy to compare a Pioneer Elite Plasma display to a Sony LCD. It is not so easy to compare two preamps.
II. Lack of awareness
A lot of people don't know this stuff exists.
III. Price
Most people can't afford, or don't want to spend that much.
I think part of the problem with the hobby is that people spend too much time on the gear and not enough time on the actual listening experience and the music.
If you really want to impress someone with your system, put something on that they like and that you know sounds good. When I want to really show off I put Bob Marley's Legend on. I once had a party in a dorm room and I put that album on my B&W speakers and I got compliments on the sound by college girls, of all people. Make your own demo CD for when friends come over.
The problem is that there aren't many compact discs that can hold up under the scrutiny of a high end system without some very sophisticated filtering or upsampling. Not recordings, compact discs. I did not realize this until I heard some of the dCS upsampling gear, which upsamples to DSD and remedies a lot of bad CDs.
If you want to impress the uninitiated, you need a system that you can play really, really loud without becoming distorted or irritating. I think as audiophiles we take for granted the ability to reproduce music accurately at high volume levels, but this is one of the main areas where an audiophile grade system will just kill an off the shelf bose or iPod. Find some music that sounds good really loud and play it.
I don't think it is unreasonable to want share the audio hobby with others, or at least to have the time and effort you put into building a system acknowledged by friends.
In my experience, however, most people even after hearing an awesome system don't even inquire about it. On the other hand, I have had a delivery driver from a chinese restaurant practically force his way into my apartment because he caught a glimpse of my speakers and just had to find out more.
There are so many barriers to entry to this hobby that it is amazing there are as many audio products as there are.
