Modern firearms are pretty damn safe as far as they will ONLY fire if one pulls the trigger. It's extremely unlikely a firearm will discharge due to being dropped, stared at angrily, etc. I heard on the news a few months back something like "the man dropped the gun and when it hit the floor it fired and killed his wife". No, he was just sick and tired of his wife's bitching...
A trigger guard is essential to carrying safely on your body(or off your body). Personally I don't like carrying off your body, say a back pack, in the glove box, whatever. I feel more secure with it on me. You're going to have to put up a good fight to get it from me, rather than bust a window in my truck and take it with no struggle, etc.