Why should we tip the hairdresser?

This is an area I have always found a bit ludicrous,whilst not tipping myself and seein g others do it............and now hearing the amount many of you tip with.......I feel truly mean.

I have had the same young girl from when not much more than newly trained to now being the owner of 2 franchaises.
This amounts to 20+ years
The overall owner of a string of these salons no longer works himself,has a swanky home and drives brand new Porches.
His charges are high and when one year he again put them up I complained bitterly as by then I was an OAP......and I walked out.
I was "sought after" and given a special concession of £20 for a shampoo,trim and blow dry on my very short hair..........and this I continue paying my lady H/D.
Tipping has never been an issue although I either pop a few tenners in with my Christmas card or buy a small pressie,whilst I will add a £5 in the jar to share amongst the shampooist etc.
There is always a warm welcome and the drink of your choice brought to you.
You have me reconsidering my initial thoughts,perhaps I should tip and be a little more generous, taking into account the entire time I spend there once a month.

My hairdresser leases her premises to another girl on a Wednesday , this is the day I know I have a sitter so have had to get my hair cut then , but it isn't as well cut or shaped , I have been tipping this girl even though I don't like the result . I have been negotiating with eldest GS and hope to get a decent cut next week while he does sitter...... but I am not going to tip

Because I have to tip GS !