My dad worked in pharma sales for 30 years. Do you think he cared to sell the drugs? I mean... in that the drugs were helping people, he was happy. But his reason for going to work everyday was talking to his colleagues. To this day, he and his old colleagues still visit each other, still party together, and vacation together.
When I tell my parents that I do things like work on programming projects outside of work, they think I'm crazy. Being genuinely interested in the content of your work so much so that you'd do it outside of a job is unique to engineering professions, IME.