The first experience!
The first experience that a person has with crossdressing is likely to be very sexually exciting, and he will more than likely carry on with the practice and will do it in secret.
If he is married he will wait until his family is out of the house, and then perhaps take a hot perfumed bubble bath, shave off his body hair and after slipping into something silky and sexy, masturbate.
Both men and women have historically cross-dressed in order to disguise their true identity, but today it is much easier for women, because the wearing of pants (trousers) and jackets etc. is now acceptable in modern western society.
In the past women often did it because they wanted to take up male-dominated or male-exclusive professions, such as military service, whereas men might have cross-dressed to avoid it.