We invented PHP and FastCGI mainly to get away from the performance hit of starting a new process just to handle a web request!
It was only a few years ago that I realized that modern hardware means that it really isn't prohibitively expensive to do that any more - this benchmark gets to 2,000/requests a second, and if you can even get to a few hundred requests a second it's easy enough to scale across multiple instances these days.
I have seen AWS Lambda described as the CGI model reborn and that's a pretty fair analogy.