I have a mobile groomer and I tip her $10. I like her service, she always does what I ask, I'm always happy with it so I want to keep her happy, she deserves the extra $10.
My mom is the owner of a salon, she does waxing/facials/etc and they still tip her. She actually makes less than most of her employees. Simply being an owner of a business doesn't necessarily mean you have a lot of money, or don't need or appreciate the tip.