Boys going shirtless

I recently happened to read a question on a separate subject and different discussion group online from a 13 yo boy who asks this question. "When I'm shirtless in my yard, sometimes girls from down the street walk by and look at me. Why do they do that? Is there something wrong with me being shirtless"? My response was to say that........ when I was young (I'm 50s now) that it was not uncommon for boys to be shirtless in the summer whether they were shooting basketball, working in the yard, jogging etc. Of course at pools and beaches its totally expected for boys (and men) not to have on a shirt but I acquiesced that things have changed over the years and that indeed you don't see near as many boys taking their shirts off in the summer months when they're playing or mowing the grass etc. as in days past. (This particular discussion was not in a nudist setting so I didn't get into the whole aspect of nudity because that wasn't his question really AND it just wasn't that type of forum to get into something that can be debatable in certain groups of people). I went on to say that these girls are probably not used to seeing a boy shirtless in his yard or on the street , that they see it as kind of a curiosity thing AND that if he's a fit and good looking kid, they're probably checking him out as its their way of being a little flirty. I also suggested that he keep doing what he's doing and went on to add that it was sort of a male bonding thing by adding the situation of say a group of boys playing soccer on a school play ground after hours. If one boy takes his shirt off, many of the other boys will follow suit and that it has a connection to some primal male bonding and bro moments. As a male, I do actually do pretty much understand and believe that. But other interesting responses came along and one actually got my attention. One particular guy said it had to do with historically men were functional dominant and non self concious. As animals a male shows he is in charge by not wearing armor. In this case - shirts. That its an expression of "I'm comfortable in this surrounding and have no need to prove anything.". Then he went on the refer to the impulsive situation of boys taking off their shirts at a sporting event and that is was a male expression of bonding (which is basically what I said). But the first part of his answer did cause me to think and perhaps I do see its history of perhaps being related to some sort of male dominance thing from eons ago. Now...keeping OUR opinion of nudity out of the equation and simply taking the question by its own merit and not pushing our lifestyles on a non nudist 13 yo, I'm curious to see what you folks think and how you would have responded. Go!