I hate to break it to you, but learning does not stop after you graduate from college.
A study done by PewResearch in 2018 stated that the average American reads 12 books a year (let's say a book a month), but those that read above the median were classified in the higher income brackets. This begs the question- do people who earn more money read more, or are they earning more money as a result of reading more...
I believe the latter is true and here's why: The pursuit and acquisition of knowledge places you on the cutting edge. Not only are you expanding your mind to new ideas, different perspectives, and training it to retain information, you are also exploring ideas whilst forming your own viewpoints and opinions about various topics. If you are not constantly seeking knowledge you remain stagnant.
Bill Gates (Net-worth: $78-billion) states that
"Reading is still the main way that I both learn new things and test my understanding." (BusinessInsider)