Because using incorrect terminology makes us all look uneducated to those antis who read these forums, thus perpetuating the myth that gun owners are "ignorant rednecks"?
Because taking a moment to use the proper terminology is the right thing to do?
Because we have so many new folks coming to guns for the first time in their lives and we shouldn't be confusing them?
I will agree with you on this, but sometimes you have to consider your audience. If you get too caught up in proper language you are always in a battle with ignorance. Look at modern language in general. Do you want to try to fix that? If you insist on all the proper terminology you may appear to be obsessive-compulsive or whatever the proper diagnosis is.