Well, if you're referring to the NG staff portraits, Street Fighter was a significant theme there, so it makes sense for most of the characters to be pretty ripped. Also, none of those would really count as self portraits other than Utah's. There are entire periods and schools of art that make an effort to idealize the portrayal of the human body. Art in general is very permissive of exaggeration.
Making a self portrait portrait that's physically stronger than the artist is not necessarily hiding behind anything. Maybe they're trying to externalize an inner beauty that they see in themselves, implying confidence and a positive image and not even necessarily arrogance. What you described is also a valid point, but I don't think it's fair to make the generalization that everyone who does those kinds of things has some sort of inferiority complex.
saltovergray
Yeah thats a little wierd. But i will break the crowd! I am so wimpy!! I am tiny and puny!! I won't make pictures of me buff and stuff because it would be a lie!!! FREEDOM OF SPEECH!!!!
FireNuke
if i draw my self im always lanky, never buff, i dont look like that D: