Starting a company needs a lot more than those three skills. Plenty of people choose a pay packet with less stress.
Many founders recycle into tech jobs after they discover exactly why failure rates of startups are so brutal. Apparently 15-25% of employees aged 30–39 at major SV companies have a failed or acquihired startup in their history. Golden handcuffs can appear very pretty after you've missed out on striking gold by yourself.
I'm not arguing what defines inefficient in these situations, just that "if we group together we'll be okay" for tech workers will go about as well as 1960's longshoreman unionization