The game has changed.
Today's car buyers insist on power windows, seats, a killer stereo etc. Even the el-cheapo "economy" cars come with a/c and cruise standard.
Look at the selling points for the collector muscle cars. 2 data plates means twice the money because of the options that are now standard equipment.
And regulations play a big part. Think of how fast this thing would be if they could drop all the airbags out and still get it insured. That said, it is an amazing piece of engineering but I wouldn't want to drive one at 140+ on the track without a roll cage!