Each of the Mexican players was given nine uniforms, three of each color combination. So only a few of the uniforms ended up in the trash.
The official excuse given by some of the people involved is, they had to discard some stuff to stay under the weight limit.
Here's what I think is really weird, though; a couple of gloves were left behind, too. Those gloves cost $200. If I were a touring musician, there's no way that I would even consider leaving one of my guitars behind.
I think that this is a all about people who just aren't very smart, as opposed to being unappreciative of the honor of having the Olympic experience. I can see why they wouldn't want nine uniforms as souvenirs, but those unis would have some value to collectors. And even if you already have several of those expensive softball gloves, there's always going to be a teammate or a friend or family member that could use it.