This is a profoundly ignorant question to ask:
- Lawyers do essentially have to practice law in their free time. Many, many state bars require continuing legal education in order to remain barred. Can you imagine having to pay money for classes or be legally prohibited from programming?
- This is also true for doctors and nurses. Continuing medical education is mandatory for both to be allowed to practice.
- Most professional academics spend a huge amount of their "free time" thinking about their field, reading journal articles to stay current, and taking classes to stay current on new statistical software, programming skills, etc.