I do the same thing.
Sometimes it's the doorknob. Other times it's a cracked switchplate they never think about. Or just straightening up the porch light.
Years ago, I was packing up at the end of the day when my cell phone rang. It was an elderly lady who had lost power in part of her house. I got directions, and it turned out it was right on my route home.
So I stopped, and a pressure washer she was using had tripped the bath GFI (GFI breaker that fed other parts of the [older] home). I reset it for her, and all was good. She asked how much she owed me.
I replied, "I can't charge you for this. No trouble at all, and it was on my way home."
Now, I can hear a lot of the business guys cringing and groaning, but ever since she has been a regular customer. Nothing big, but always calling every 4 or 5 months.
Maybe she should have a heart-to-heart with the bathrobe lady.