Rusty,
A lot of us older folks have been here for a minute or two, but yes 1st time i heard DM and was like what the hell is that? Now I understand new generations, and new phrases and a little bit different communication methods.
I tip my barber, pizza delivery person, and in restaurant's where I sit and enjoy a meal. As others have stated, the vast majority of every other situation it's their job in performance of normal duties.