Generally speaking, the "artists" name is already on the front of the head stock in a well-executed manner.
I think you're mistakenly equating a trademark or logo with a maker's actual signature. Those are very different things that are done for very different reasons in my world.
But there's many people these days who freak out at the thought of getting involved in any sort of personal interaction such as have a face to face meeting - or conducting a phone conversation with someone. So it's hardly surprising that the thought of some luthier adding their own personal hand inked signature to something they're selling could be a complete turnoff for a certain sort of customer.