There are many who through circumstance or poor (or good?) choices ended up with the crap job but nevertheless pay attention to the larger world around them learn as much as they can. Maybe they studied history and are working in an Amazon warehouse. There is a lot of "squandered" intelligence and curiosity and unapplied ability in the non-knowledge-worker workforce.
There may be some people above the level working those kind of jobs but most are not really what you would called untapped geniuses. These are folk you can't rely on pressing a few buttons in the correct sequence when the situation is life threatening. Guesstimate : a lot of them are sub 100 IQ.
Educated people working in professions which select related to IQ get surrounded by other high IQ people they forget what the other side of the bell curve looks like - despite the liberal blank slate fantasies all people don't have the same potential, a big % is genetic/predetermined and those people are much more likely to end up in the low income bracket (income and IQ are highly correlated, and heritability of IQ is significant, and things like parenting are not other then being potentially detrimental).
I have a degree in computer networking that I've never used. Most of my job experience is working retail. While working retail, I've found time to put into doing software development as a hobby.
They still would have not decided, if the food on the table thing wasn't pressing, that they should get a job on Amazon (warehouse) over it.
Of the people I knew who frequently read or studied things in their spare time, one quit to become a pharmacist and the other now works in IT last I heard. And then there's me.