Potatoes grow under the ground, in dirt, which makes them dirty. (This is science.) If you are going to eat the whole potato—skin and all—you should wash it beforehand. Baked potatoes, roasted potatoes, skin-on fries—all of these spuds need a good scrubbing as a first step, before any further prep work or cooking is attempted. But if you’re going to peel a potato (for a mash or some other skinless preparation), there’s no need to wash it first. Just give it a quick rinse after you’ve peeled it.
Look, you’re a busy person, and you have things to do! Why waste your precious time scrubbing dirt off of a surface you are going to remove wholesale with a knife or peeler (preferably a y-peeler, the best peeler) a few minutes hence? That’s extra labor and, unless you are being fairly compensated for it with an hourly rate, there’s no need to prolong the task of potato prep. Besides, no matter how hard or how thoroughly you scrub, little skin bits and flecks are going to stick to the spud, so you have to rinse it anyway. And for what?
Streamline your potato process, babes. Just peel the dirty potato, toss those peels in the compost, then give your peeled potatoes the quickest of rinses. Peeled potatoes are slippery anyway (thanks to all that starch), so the dirt will slide right off, no scrubbing needed. Then you’ll be ready to mash and smash your way to mountains of fluffy, creamy mashed potatoes. Or make the Taco Bell Taco Pie, aka two Taco Bell crunchy tacos buried in mashed potatoes that have been flavored with Taco Bell sauce packets. The choice is yours, my friend. Choose wisely.