The great majority of them are taught from a young age, either by parents, sisters or female friends to invest in their looks and so they do. When they approach 20, many of them can easily have over 10 years of exerience in investing in their looks, while many boys still just wear whatever hoodie their mother bought them. For them it is a great investment of their time to sit on youtube learning different ways of applying make up and learning fashion, they know their status and ability to attract the opposite sex with this keeps growing.
Many boys never learn anything like that. Hell, so many adult men have never put an effort in their looks, it's all about performance, money and the status derived from that.