I am pretty sure the Ray/Beef business in the last strip is Ray giving Beef a particularly aggressive "See? Ain't no harm done and I made a dude hella joyous! This dude who works for the grocery store and he don't mind it none at all!" look and Beef replying with an "Okay, dude, whatever, chill" stance.
Ray buys his own groceries because it's all about the whims, man. Impulse snack buys, that's the thing. For Real Meals, it's class all the way: meats special-ordered on rush delivery from one of a dozen specialized butchers, pet-cultivated fruit and vegetables from Japan, and there's this one rice-grower dude in Colorado who does crazy stuff with hydroponics or something. But when you want Lucky Charms, beef jerky and a sixer of Whateverbrau? Supermarket time. And then maybe like the new Chipped Beef Pringles catch your eye, and you just go with it. It puts the Pringles in the basket.
I do not have any actual moral outrage against eating in the store, but I could not bring myself to do it. Much like the ex-Jew who still, decades later, cannot bring himself to eat pork, the habit is too far ingrained.