That's so true! I used to love to learn... I mean I had to learn Spanish in 6 months when I moved to Costa Rica for an internship. Plus I've read at least two books per month for the last 3 years (business and psychology stuff). But learning to code was a lot more exhausting because it's based on knowledge and there's no room for bullshitting (unlike business ;)

There's a big difference between the kind of "learning" that is absorbing a lot of data (reading business books, studying chemistry, reading history) and using that data to draw solid conclusions. The former is kind of fun, in the same way that watching TV is fun. It can be mildly entertaining, and your role in it is mostly passive. The latter is hard work, but yields a much better high on success. I don't think the pleasure is due to the greater effort. Instead, it seems to come from the awareness of the new vistas you've managed to unlock.

Programming has elements of both kinds of learning. You need to learn the rules of syntax. You need to understand the libraries you are using. There are plenty of other basics that you need to know, but aren't particularly satisfying to learn. But once you start solving problems, the experience is very different. In your fist six months, everything is new. Your sense of achievement is great. As your skills expand, more of your work is simply good engineering. Unless you are constantly pushing the boundaries, your new discoveries are more limited.

TL;DR: reading business books is comparable to studying programming libraries. Successfully executing a business deal is more comparable to building a MVP.

I think that this is more and more true of most any job, though certainly programming is in the forefront.