The supermarket workers you are talking about are primarily in the Meat, Fish and Deli counters. As such, they handle a wide variety of raw meats, so using fresh disposable gloves for each meat is the easiest method to prevent cross-contamination between meats.

yes obviously

In McDonalds, some disposable gloves are used when handling the frozen raw patties. Once cooked, the cooked meat (and chicken etc. products) are only handled with tongs, which are coded such that each meat has its own set of tongs.

I consistently see McDonald's workers putting burgers and stuff together with bare hands, touching the meat and vegetables and everything.