It's one of the benefits of the software. If a thread you are participating in gets a reply, you normally get an alert, unless you have turned that function off.
Quoting is really best when you want to pick one part of a post out or if you have multiple posts (not necessarily from the same person) that you want to address.
I find myself guilty of doing it also sometimes. I really hate it when someone says something and it really doesn't tie directly back to anything in the thread that you can find an association to.