> an activity or interest pursued for pleasure or relaxation and not as a main occupation:
You're basically positing a definition of "hobby" that encompasses everything that isn't working. Caring for children is a basic life function and an obligation. It can be relaxing and pleasurable, but so can showers and eating--that doesn't make it a hobby. Hobbies are things you do optionally.
> Caring for children is a basic life function and an obligation.
Contraceptives exist and work (for the most part), so caring for children is an opt-in activity.
And even if it wasn't - it is totally possible to turn cooking or eating into a hobby by going beyond what's necessary to survive, and the same applies to caring for children.
As a late-twenties programmer without children, I'd have a lot of respect for anyone who mentions his/her kids as his/her hobby.
You're basically positing a definition of "hobby" that encompasses everything that isn't working. Caring for children is a basic life function and an obligation. It can be relaxing and pleasurable, but so can showers and eating--that doesn't make it a hobby. Hobbies are things you do optionally.