Male Crossdressers: Why do they do it?

They do it for the same reasons most people do things; there is something in it for them. This is usually emotional pleasure, sexual pleasure, reduced stress or a mixture of these.
For male to female crossdressing to be rewarding there is often an experience earlier in life where female attire is unconsciously associated with sexual or emotional reward and sensitivity to forming that reward association.
If you consider that the object of sexual desire for most men, “women” often express their sexuality through clothing it is easy to see why men might form this association. If you also consider how polarised gender is in many societies, it is easy to see how expression of femininity can be a welcome break from the stress of trying to fit all the stereotypical male roles.

What determines how open or closeted they are?

There are also a number of other factors that may determine the extent someone will go to, to outwardly express their cross gender clothing choice.

Confidence: Fear of social ostracism or humiliation stops many men from expressing their choice to wear female clothes. A person with high self-confidence is less likely to be influenced by this and therefore more likely to crossdress openly.

Social acceptance: A society that legally punishes “female impersonation” or a family that will cut you off if you do not conform to the stereotypical gender norm is a huge deterrent. An accepting society, partner, friends and family make it much easier to crossdress openly. Despite many societies becoming more accepting of crossdressing recently, many crossdressers carry an image of less accepting times. This bias keeps many crossdressers closeted, fearing a world more hostile than it actually is. Many experience a huge relief when they discover the reality.

Feminine Attractiveness: The more feminine and attractive a crossdresser can look and behave the more acceptance they will get. People are less likely to challenge a crossdresser if they are not sure, as they fear embarrassing themselves. Men are more likely to be sexually attracted to the crossdresser and behave more helpfully, though this can also backfire if a man feels his own sexuality threatened. Women are more empathetic if they sense a deeper femininity. Feminine attractiveness can be improved with skill and for some, surgery.

Age: Once past the age where attracting a woman into one’s life to form a family is a priority, men can loosen their hold on the male role stereotype and more comfortably explore their female side.

Social Status: Most men seek social status, knowingly or not. Social status is one of the most powerful tools for a rewarding life and one of the most powerful attractants of women partners. In many western societies crossdressing has a negative impact on a man’s social status. The higher mans social status, the more he has to lose by crossdressing and the greater the need for secrecy. However, if a man attained social status by artistic or other productive achievement, they will are more likely to maintain social status despite openly crossdressing. I’m sure you can think of a few male pop stars whose less than masculine image did not seem to hurt there popularity.

Identifying as female: Many people categorised personality traits as stereotypically feminine or masculine. The clothes one wears is one of those traits, so is preferred gender of sex partners, and dominance or submissiveness another. There are many. Some genetic males due to a combination of life experience and biology may identify with enough female traits to self identify as female. For them, dressing in female attire may not be crossdressing so much as expressing their true gender. They usually get a greater emotional reward from crossdressing and some may even choose to take a path toward transsexualism and living openly as a woman.