Did they have protien shakes 40 years ago? Where there strong muscular men 40 years ago?
You don't need shakes. In most, there is nothing in them that you can't get from food. What makes them so desirable is convienence. Easier to make than a meal, more portable, no guesswork on the nutrient breakdown and easier to take (tastes great, less filling).
I don't consider protien powders or MRPs in the supplement group, I'd say they are just another food source.
If you stop them or not, is a choice left to you. Besides cost, there is no reason to stop, or cycle shakes. Even thinking about cost, cost per gram of whey versus food source protien goes in favor of the whey powder.