I think maybe you did not understand my original reply. You do not typically use the content of undergrad courses directly in the “real world”. You become more generally intelligent by studying. Just like you wont bench press weight outside the gym but you benefit from the exercise in the gym. The exercises help you build muscles you use outside the gym. You use your intellect outside the University. You can exercise without the gym and you can build your intellect outside University, they are just very useful options. A Masters or PhD would be the deeper study of specific content.

And I'm telling you that having read applied mathematics at one of the best universities in the world, I wish I didn't. I don't think I have improved my intelligence by having gone through it, and when I meet recent graduates (especially Americans) I'm always in amazement about how little they know about life.