Tipping independent owners

Tagging off the earlier post about tipping culture.

When is it ok not to tip? I take my dogs to get groomed once a month or so, the lady runs the shop out of her garage. I never tip. Should I?

I went to get a massage, again a one man operation, and I didn't tip. Should I then?

I've always been under the impression that tipping is done when it's a situation where someone is using someone else's space for their work, so say waiter, hair dresser at someone's salon, that kind of deal. And not if the business is their own and they're the sole employee.