5-man Dungeon Finder PUGs follow a predictable pattern through patches. At the beginning of the patch, when the content is fresh and new and (in some cases) difficult, puggers are talkative, helpful and generally more friendly. You just wiped to Queen Azshara? "Hey," a DPSer might say, "we should kill the Hand of Azshara as priority." "Ah, I see," the tank replies. "I didn't know -- sorry, I'll put a skull on it."
Now, that may well be either my being lucky with a PUG I was healing or my memory distorting past events. However, it seems that as patches progress, talking in PUGs becomes ever rarer and ever less kind. At this point, you're lucky to get a "hi" at the start of your PuG, and if anyone does talk about the Hand of Azshara, it's most likely just someone spammming a macro that yells "HAND." I think the same behavior holds true in the Raid Finder, too.
As you may have noticed, I am a talkative soul and often try to chat in PUGs. I'm generally ignored ... but it hasn't stopped me yet! So would I drive you round the bend? Are you just there to get a job done and don't care for pleasantries or making a connection with strangers you'll likely never encounter again? Or do you long for a bit more conversation? Is silence golden in PUGs?
Also, a personal gripe -- is it so hard to reply "r" when asked "r"?