You definitely haven't taken a cab in big cities in US. Cab drivers always speed. It is what they do - I don't know why - but driving below 75mph is not within their realm of possibilities.

You also haven't taken a UberX ride from looks of it. If you did, you would realize that they never ever speed and are very courteous in their manners!

I know it sounds strange - that professional drivers speed like mad dogs and are at many time disrespectful while random people like you and me are better/sane drivers - but it is what it is. Uber does a great job weeding out bad drivers through their rating system - unfortunately cabs can't do that..