Plain to me has always meant just burger and bun. I've never been delivered anything else except when it hasn't been properly keyed in. Back in the 80s when I was the only one on the planet who wanted a plain burger (that's what Mickey's D's would have had you believe anyway), you had to wait forever to get your food. I'm glad most places are more "cooked to order" these days. I hated waiting at the table while everyone else had their food already.