Keep in mind that many folks do use an additive to the media in their tumbler, and an additive that isn't just an abrasive, but one that lays on a microscopic coat of wax or something on the surface of your brass. For example, Nu Finish fits this category. Then your cases are most likely lubed enough, although another quick shot of a very light coating of lube doesn't hurt in my experience.
I can remember years ago sizing unlubed .45 ACP brass tumbled without additives in a Lee Classic Turret. It was even making different sounds as it entered/existed the die along with the harder pull which didn't give me a very good feeling. I haven't examined the die closely, but I bet there was some galling taking place - carbide or not. Then I started to just damp my fingers with the Lee paste lube while handling the cases and just that little microscopic amount made a world of difference. I don't bother now because I use additives and also use the spray lube on cookie sheet technique for large volumes of brass.