Not be in the business of doing something
Definition 1 of 2
Pro Tip 1/3No Responsibility
Used when denying duty or obligation in a situation. 
As an accountant, I'm not in the business of giving legal advice.
Pro Tip 2/3Figurative Speech
This phrase is often used metaphorically rather than literally. 
A gardener saying they're not in the business of weather predictions.
Pro Tip 3/3Deflecting Involvement
It can indicate refusal to be dragged into matters outside one's scope. 
I'm not in the business of mediating family disputes.