That doesn't always work, depending on the shape of your head, the texture of your hair, etc.
I for one don't care about it much, and my job allows me not to care, but many people do care for both personal and professional reasons. Any kind of job where you want to persuade people basically requires the best look you can afford. It's basically an investment.
Gah to think of all the times I managed to fail to persuade people because I have short hair :)
To me it is a mix of feeling that spending money on cutting my hair is wasteful, spending time to go to a hairdresser is wasteful and so on. It's just a maintenance chore. And I don't feel it has ever caused me to perform subpar in my job or to have people take my arguments less serious. But I can see that form some people this might be the case.
In a way this is a luxury that men can afford themselves, if a woman would go to work with a very short hair it would immediately count as some statement rather than being efficient.
I for one don't care about it much, and my job allows me not to care, but many people do care for both personal and professional reasons. Any kind of job where you want to persuade people basically requires the best look you can afford. It's basically an investment.