The reason you have a skin at all is so other minecraft players in your world can see you. The reason it is Steve as opposed to a different-looking character is because Notch programmed it that way, and he hasn't told us why.
Steve. (reference skin)
you can use skin edit and make him
Steve(the normal skin) and Mr.Creeper(a creeper with a suit).
You can't. The skin you have before you upload one is called "Steve"
there is no real explanation to who he is, he is just the default skin, nothing more, nothing less
You will need to find a smiling steve skin.
The default Minecraft character/skin does not have an official name, but in a very old blog pst, when Markus "Notch" Persson (Minecraft's original creator and developer) was asked what the character's/skin's name was, he replied "Steve?" Since no players really know what the name of the character/skin is, and they only have this information to back them up, most players name the character/skin Steve.
Steve
Not "Everyone elses" The dark skin is the default skin, nicknamed Steve :P You can easily change your skin.
Currently the only default skin available is the male skin, named "Steve". However if you purchase the full version of Minecraft, you will be able to upload your own custom or a pre-designed skin.
Depends on People's preferences. Steve (technically) is most popular (default).
Currently, if would have to be the default, Steve. , or notch skin with the cape mod too. Really, its what skin is most Downloaded to date