I have also noticed several rather useless replies lately, but I don't know that the ratio is substantially worse than a year ago. I'm also not convinced that you can divine that the reason for posting tersely is to gain XP quickly. (Hey, sometimes I post one-liners, and I can't tell you the last time I looked at the rating of one of my posts.)

To make a short post longer, I agree with the premise of being silent if you have nothing to contribute, but I think your judgments are a little careless.