It's a big reason why it's being done. As I've said, if you're Jewish or you truly believe that there are medical benefits to it, then go right on ahead. I consider those valid reasons (though I disagree with both). However, I think most people do it just because it's become the norm in this country. It's also rapidly becoming the exception here, as most doctors are now advising against it as a routine procedure.
But doing it because it is the norm isnt the same as "why not?" Conforming to the norm is a valid reason.
That's an interesting point, and I suppose that you're right that it's not the same as "why not?" However, I have to disagree that it's a valid reason. If we're talking about getting you ear pierced or something similarly mundane, then OK. We're not, though. We're talking about performing surgery to lop off a piece of somebody's dick. I think that deserves more consideration than "well, everybody else is doing it."
Furthermore, we're talking about an elective procedure that the child has no control over. I'm all for a parent being able to make decisions for their kid, assuming it's a decision that needs to be made. If we're only doing it so the kid will look like everybody else in the 24 Hour Fitness lockerroom, then what's the difference between circumcision and getting him a tribal tat on his arm? Being elective, it's the sort of thing that he should have some say-so in.
Lastly, it's an artificial norm. If the kid had a second nose, then nobody would suggest making him live with it until he could decide whether or not he wanted to look normal. In this case, though, we're talking about modifying him from the normal state of being a human male into something that American society decided should be the norm.