I am interested to understand why programmers are often so intensly passionate about coding. One obvious aspect is certain economic prosperity that the profession brings, but money is only (small?) part of it.

Programmers often work hard on personal and/or open source projects in their spare time without any financial benefit. It would be difficult to find accountants spending weekends on their personal accounting projects or any other professionals seemingly always working outside of their paid jobs.

So, what is so special, enjoyable, engaging about coding?