Yes people do that, but there are also a lot of writers that saying something like "I have this great idea but I can't tell you unless you're x-amount qualified and are super interested in it based on the three sentence brief I whipped up before I can show you my holy grail of a script."
Those same writers then complain about how everyone is ignoring them and being an "ass".
I've been on this forums for a few years now and I'm confident in saying that every writer who has pitched his/her idea in a professional manner (with previous experience, well-thought ideas, scripts uploaded and ready in a shareable document) have been met with professional treatment and interest.
On the flip side, writers who pitch like it's just a hobby or something on the side, artists treat it as such.