I can’t think of a single job/career that can’t be mastered with some ‘study at home’ and a spell as an intern.
How do you prove to an employer that you've "studied at home?" Why should an employer even start with your resume without some educational credentials that show you've done some critical thinking, are functionally literate, and have shown that you at least have the tenacity to spend 3-5 years in pursuit of something?
And as far as internships, what company would invest the time in training someone without some proof that candidate can learn? This is particularly true for positions in the medical field, law, and engineering, to name a few.
Think harder.
You bias is supported by your ignorance.
I can’t think of a single job/career that can’t be mastered with some ‘study at home’ and a spell as an intern.
I'm guessing that you have not finished either a B.S. or higher degree in the physical sciences or engineering and attempted a highly technical profession. As one who has done these things, I can tell you that my undergraduate and graduate studies prepared me in ways that home study and on the job training did not. I have never seen someone at the top of one of these fields without an advanced degree.