And let's face it - the sort of businesses that HN readers want to start up are rarely that simple. Most people here are dealing with equity, vesting, cliffs, angel investors, VC money, cross-state and international taxation etc. We're not put off by something being a bit harder. Why should other people be?
So, while you're right that there might be fewer businesses, the EU doesn't actually stop people starting if they really want to.
It's also worth pointing out that if someone is falling at the hurdle of just registering and starting a company then the chance of success is very low. There are going to be much harder challenges ahead even where company formation is complicated.
It's also worth noting that some parts of the EU make it a lot easier to start even than the US. Estonia's e-residency programme makes it incredibly easy to register for limited citizenship and start a digital business based there.