The gag is more or less no different than the western portrayal of guys as lazy, short sighted- everything can be fixed with duct tape and beer sports obsessed knuckle drager. It just stands out to us more in the west as being out of place because it's a trait not really noticed in our cultural entertainment, or even how we are. Curious about this I spent a great deal of time talking to a few of my lady friends in Japan . I more or less pieced together most of the reasoning long before, but wanted more solid backing. What I was told is that over there young men are considered timid, often lacking confidence and over saturated with noble ideas of what a man “ should be” but so beat down to a level of conformity that any ability to mature in “ that” area is more or less neglected.
Women on the other hand have taken the more western path and become more aggressive and assertive- which obviously makes the whole timid issue worse. It's naturally played up more in a entertainment medium, but there you have it for those wondering. As annoying as it may be to some of it, it has it's place along side any cultural stereotyping digs we all have.