Peer pressure;
Positive self & peer reinforcement by just looking at the bike (you can see what you spent right there and so can others-boys and toys);
Perceived cool/competence factor (i.e. you must be a FAST rider, just look at that can!..)
Some people follow the herd and can't/won't think for themselves or admit it
Think the "incremental improvement is not worth the money" because they haven't tried it. I didn't try it but I valued the opinion of some of my peers who did. And it IS worth it.
You can re-sell it if you don't like it (probably doesn't happen as much as they think) or sell the bike-can't do that with the Flash.
It's all about others, the Flash is all about the rider experience. (I think it's true about a lot of things, but most of my riding is pretty well all about me anyway, so who cares).
Flashy can you can see vs practical mod that you can only feel, not see (see the gaudy riding leathers, helmet graphics, ugly gloves, etc.- more boys & toys- okay with me, not my style). How gaudy is the Aerostitch gear?
Style itself - Who are the Two Brothers and why should I care? Wonder if these guys used to hang at the mall when they were kids?
(See point about practical above.)
Last: Loud Pipes Save Lives (they secretly wonder if it's true...)
Ron