Surely the workplace may've been willing to negotiate one unpaid afternoon off a week to:
* volunteer as a coach for a childrens sports team, or
* participate in rehearsals for community theatre, or
* volunteer for meals on wheels, or
* participate in a community garden, or
* some other community oriented task
But a hobby is simply one's own interest and thus the workplace is less likely to be as accommodating.
There is however a gray area where the lines between hobby and comminuty involvement get blurred - such as being a member of a medieval reenactment group for example. Some people would consider that simply a hobby whereas others a community pursuit.