EL IMHO. Tip pushing is usually done by the individual lady as opposed to an in-house rule. Some feel that they can get more than the standard rate if they try. But every place, every provider, and certainly every day is going to be different.
Many Many years ago a buddy of mine had some business cards on him for certain unsatisfactory times..
" The tip would be bigger IF the service was better " Gotta go to Kinkos and get me some.