Because not all are here to listen and follow good advice. Some just forget about it and continue doing what they think is right.
In fact, we have to be thankful to those old traders for sharing how they stepped out of their mistakes for us to change. Unfortunately, instead of doing what they say, we do the opposite and commit the same mistakes that the old traders did before. I could say that no matter how much advice we give, nothing happens if we don't see it as valuable. We are still doing wrong before we learn something.
It is better to learn through the mistake of others, than to have a bad experience. I suspect that the reapn why some trader don't take advice from experience ones is because of greed. They want to make quick money from trading, so they end up taking uncalculated risks that can lead to big losses. Some of them end up learning their lesson the hard way when they suffer losses. I am not an active trader because I have not gained enough knowledge to start my trading adventure.
Those who are new to trading are very wrong in this kind of activity, that after gaining general knowledge about trading, they become desperate to achieve success in trading, and they start using a lot of money in trading without adequate advice. Trading is a field where the possibility of loss is high if patience, knowledge, and rules are not followed, moreover, trading is more difficult than we imagine, so here we must definitely take advice from an experienced trader. Learning from the mistakes of others is really a great virtue, it is definitely good to have this kind of mentality, but if you can learn from the real experience that you will gain on your own, that is, In the first stage you will have to face losses, and from that, If you can learn more deep from that, then it is even more effective.