I don't think it's fair not to tip 15% to a stylist. 20% is what I usually do. It's a personal service + convenience. If I didn't want the convenience/knowledge/talent that goes with a stylist's time, I would DIY (and in my case botch it terribly).

I think that any service pertaining to personal hygiene deserves a tip. Yes, I think haircutting falls into that category, not to mention the training, talent and knowledge that a customer relies on when entrusting their appearance to this professional.

The only time I've heard a customer isn't supposed to tip the stylist is if s/he is the owner of the salon. Even then, I would feel awkward not tipping, but I know that's done. JMO.
Location: Texas
Type: 3b/3c (i), below shoulder length.
CO wash: A-O GPB LYY, Desert Essence Coconut, Oribe Silverati
Leave-ins: Curl Junkie Beauti-Curls, KCKT, cno overnight
Styling: BRHG, MGA Sculpting Gel, A-O Mandarin Magic Gel, LOTD AVG, LALSG, CJ Pattern Pusha
DT: Curl Junkie Deep Fix, Briogeo Don't Despair Repair!