It is interesting that we do accept the notion of ethics and good practice in so many aspects of our lives other than Tarot. Of course we acknowledge that having both things "certified" in reality doesn't mean that we necessarily get the best product or outcome ~ but they are guides to choice.
And it doesn't mean that people who are not "certified" don't do a good job. I'm not certified but I try to do the best I can for the querent when I read. I don't take money for readings but I do the best I possibly can, in terms of preparation, content and presentation. I know others in the same situation do as well.
I don't believe that people need to be certified but for many newcomers to Tarot certification or registration with a particular association may be a guide to choice, often the only guide if people don't know anyone else. I wanted a good reader three weeks ago and, not having many contacts, the first place I went for information was the local Tarot Guild. I was not disappointed.
Sometimes I wonder whether those so actively critical of certification are not being a little over reactive. I personally don't think Tarot will ever get to the stage of being regulated in the way some other professions are (of necessity).
Is this issue worth the strongly negative feelings it seems to evoke whenever it is discussed? Not my place to judge, now, but I wonder. For some reason the feelings seem to go beyond the boundaries of mere debate, and I do wonder why it matters so much. Surely there is room for people who take either approach - certification or non-certification?
To use the awful language and concepts of today in this *free* society, the market will find its own level, depending on how good people are and how well they promote themselves and their particular art.