Don't you need a license to be a barber?

In modern times yes, here's some interesting reading on the guilds licensing originated from - https://en.wikipedia.org/wiki/Worshipful_Company_of_Barbers

And yet the US has consistently been in the vanguard of software development worldwide. Do we need surgeons? Do you need a four year postgraduate degree and three more years of apprenticeship before slinging together a web app? Certainly the industry has its problems, and some applications demand more rigor, but I don’t see this as much of a general solution.

The market didn't demand a high survival rate or efficacy for barbering either, but do you think that the (conscious or unconscious) that software engineers are some sort of magical wizards will last forever?

There may be explanations beyond wizardry - e.g. maybe barbers were historically often self-employed, small business owners who realized they stood to gain from creating barriers to entry such as licensing requirements.