It's true about not requiring academic success to have more income, it's more of grit, resourcefulness and hustle.
While having that doctorate or masteral proves that you're good academically and that's a proof that you've finished that. There are some companies that are looking for those for their higher positions.
An educational degree is proof that someone has the ability and in my opinion it is quite influential in getting a job and also the relationships that academics have will be better than others so they have a greater chance of getting a decent job to increase their educational income.
So in my opinion, higher education has quite a big influence on the income you will get, and one thing we need to remember is that we cannot compare several people without successful education, we have to be realistic in looking at the average number for a conclusion.
There's a balance on these things while having no degree or any higher of that and if someone who's in that situation is having more income, that person was built through time and tested by his experience.
While on the other side of having a degree and other academic achievements, that's actually a good start to build a career and being hired is giving the higher chance because of it.