Why do guys think it's a sign of weakness to cry?

I honestly don’t understand why guys think it’s a sign of weakness to cry. I do know a few guys that don’t try to hide their feelings and embrace the moment and cry at times of sadness, and most of time, people will thank them for not trying to be a tough, emotionless ‘man of steel.’ You cry when the pain is so deep, so heartbreaking, so true, that words can’t begin to express the pain you are feeling. I honestly think it makes guys look like jerks and that they completely don’t care at all when they just stand or sit there like nothing has happened and that its just another ordinary day. Now I’m not saying that there aren’t girls that do this too, because there are girls that do this, but the majority of people not seeming to care are guys. The only reason I’m bringing this up is because recently, everyone at my school found out that there is a junior who was recently expelled because he got into a fight with someone who said, “Pfft! Kids are stupid! Heck! I’d shoot my two siblings right through the head this instant if they were here right now!” This particular juniors siblings had died earlier that morning in a horrific fire. As you can imagine, as soon as the student body had been informed of this, everyone started crying except for a decent majority of guys. It just fathoms me that some people just don’t, or act like, that they don’t care about the death of four young children. So back to the point of all this, why do guys think it’s a sign of weakness to cry? Thanks for reading.