Cars have speedometers to tell you what speed you're going.
I think you should reword the question,. It is not why their speedometers go that high, but why the cars are electronically limited at such a high speed. A speedometer needs to tell you what speed you're going, and if you're going 130 on the freeway, it should say that, right? So the thing then is, why are cars so fast?
Sorry if I'm coming off as a know-it-all. I'm not. I know very little. I think some cars are built to go that fast just as some cars are made with interiors that sport Brazilian mahogany and pleated lamb's leather. They are that way to set them apart from the crowd, and give a person material ambition. "My car goes 155 mph". "Oh, yeah, well mine goes..." Yeah.