I guess people dont take trading seriously and hence they lose.
Exactly that -- people think trading is a joke. I have seen a lot people mention that they trade for fun, how stupid is that!? Fun and risking money don't go well together. These people either just say that to bump their post count, or they indeed end up losing because of their stupidity. If you don't take trading seriously, you'll get eaten alive.
One should take proper training and if possible take trading classes before starting yourself. If you cant pay for training, then there are many online courses available for trading. We should go through that if we want success in trading.
It isn't really necessary to follow 'trading classes or courses'. If have been building up my experience by jumping into trading directly. I swallowed big losses at first, but I am happy that I have gone that way. If I look back at what I lost back then, and what I gained (in profits and experience) right now, then it's worth every penny. I see it as an investment in myself.