Why are self readings so discouraged?

I feel as long as you are able to be objective, you’re self aware, know thy-self, and are going into it with an open mind and a willingness to listen to what the “cards” are saying even if it’s not what you want to hear, then there shouldn’t be an issue. But I see how those things are difficult for some people. I just think reading for yourself makes more sense then having others read for you. Who is better connected to you then yourself? It takes a lot of introspection but even if you are unsure of the meanings at the moment of your reading, time will eventually reveal the things you are uncertain about. Not saying it isn’t good to have some outside perspective from time to time but the narrative just feels like a way to sell more readings. Like with everything practice makes perfect.