Probably because his comment isn't interesting, isn't relevant, and doesn't contribute to discussion. There are all kinds of true but uninteresting comments one can make, but making them shouldn't be encouraged.
Edit: I'm sorry if that sounds harsh, but actively discouraging uninteresting comments is what keeps the signal:noise ratio high here.
Probably because his comment isn't interesting, isn't relevant, and doesn't contribute to discussion. There are all kinds of true but uninteresting comments one can make, but making them shouldn't be encouraged.
Edit: I'm sorry if that sounds harsh, but actively discouraging uninteresting comments is what keeps the signal:noise ratio high here.