I look at my CTSC and I have pronounced it "stupid" about once a month, but I always wanted one: so I got it. Especially if you commute in bumper to bumper traffic like I do...right along side DB9's, F430's and Ford GT's....and we all get to the next stop light at the same time. Very impressive for an NSX to hang with cars like that...
However, here is probably the most likely reason for other people:
It requires a significant chunk of money and time, the chuck is so large that it has utility for many other things. There is a sunk or locked expense of about $10K which is significant to most people. And this expense begets other expenses (extra fuel, extra complexity, extra stress and extra service).
It also takes a couple of weekends to install or a couple of weeks of net salary pay for somebody else to install.
If you have any value for your time/money: a SC is bad idea.
I think most people sell their SC's because they bought them on an impulse and really couldn't afford it (meaning you don't have +6 digits in your bank account) in the first place. At some point these folks would like their money back so they can do something else after the initial thrill wears off.
However, a SC represents the best return on HP vs Dollar Spent over any other modification. But the monetary utility of the SC cost is why people still spend $200-$1500 on very poor HP returns. (It is also the same phenomena why you are likely to get very rich selling to poor people. It takes a lot of disipline to save a critical amount of money that has high utility, most people like to just fritter their money away in small chunks.).
Bottom line: they are silly The expense of time/effort/. A stock NSX needs nothing.
Drew
