Why does Superman wear his underpants on the outside?

Raising children is the toughest job in the world, regardless how many others in different conditions are doing it. There are not even patterns that you can copy.. I mean, in my profession you would have design patterns that could be used off-the-shelf and you are happy. In human world, regardless of millions of years of history nobody has documented set of patterns for raising children. Everybody has some theory that may work or may not work. Humans are strange animals indeed.
My 6-yr old is now in the comics world. He gets these fancy ideas about being a Super Hero. So one day he is the Dark Knight, other day he is the Flash and many times - favourite, the man of steel. Even though Superman dispenses American Justice (which in today's world may not get many admirers...), the character has universal appeal. Of course it helps that modern media propogates the character in more neutral way than 1940's. The first time I saw the Fleischer series in the VCD format which my wife bought for my son, I was really scared by racial undertones of the cartoon especially about Japanese. I kind of had to 'ban' the viewing of this CD from our household. Thankfully my son does not yet know the history of world wars. In the comics world it becomes increasingly difficult when things start getting more earthly. In that sense I like the Justice League or Power Rangers better, given their job of protecting earth or galaxy.

However getting to child rearing experience, now we have to deal with more innocent questions like Super hero's dress sense. It practically looks like a gay-fair (Batman I recall, was actually called out gay in the comic book cover once !) and of course the style of wearing red briefs on one's dress is really something that all parents have to answer once in their lifetime (at least in the parts of the world where Superman media is watched by children). However cliche it might sound the answers have to be invented. My answer was because Superman may have gender insecurity and thus wants to show [it] off. My wife disagreed with me and argued that our 6-yr old may not have had time to study Freud that well. Minor detail.. but women have always winning argument, as I see it. So we went through the saving-world and graces phase of parenting. Top three(3) answers that we came up with:

1. Aerodynamics: The dress provides easy flying with minimum resistance, wearing clothes over clothes would introduce air resistance.
2. Convenience of toilet: Consider lack of toilets in earth's stratosphere and during intergalactic travel. This went very well with my son, this was something he could directly relate to.
3. Style statement: This was pretty good (and obviously thought by my wife, if you get the hint!) and something that bollywood crazy 6-yrs could understand.

Clearly we bypassed the 'suppressed sexuality' issue, but I am sure he is going to find it out one of these days and would tell us that we could have told him earlier and that we were being protective. Presently he is happy in killing aliens and is terribly afraid of kryptonite which helps us a bit in managing command and control.

I wonder what the originators thought of making Superman with underpants on outside theme. There is lot of research on Superman costume of course. Superman through the ages, for example describes that these were tatters left from the childhood of Superman that were stitched together. Given that Martha Kent had little rustic fashion sense, I submit that style statement had revealing underwear but why red? I mean there was choice of having same color as other dress. In India, VIP underwear never caught on about the value proposition Superheros had till late and when they did, X-Gen was already here to provide more view of epidermis than caped comics characters.

On many weekends I play with my son. Some times we form the Justice League, with him in Superman role. I just hope that my son limits his dress choices to himself, I have not been asked to dress for the role yet and frankly I don't care much for superpowers if it requires me to show my underwear.