Maybe it's a texture thing?
A PP mentioned she puts onion powder in. That sounded fine to me. It just flavors the mashed potatoes. Mashed potatoes should be luscious, smooth, creamy, comforting goodness.
I don't like finding chunky, slimy, shiny, chewy bits in it.
I am the same with garlicky mashed potatoes. I ate at some gourmet restaurant. I have a feeling this was one of the signature sides of the place. Only I didn't know it. The mashed potatoes were served automatically with the entree. They were overpoweringly garlicky. So, already not to my taste.
(I just like my mashed potatoes with milk/cream, lots of butter, S&P. For baked potatoes, add some sour cream. Occasionally melted cheese.)
But, when I found chunky bits of garlic in the mashed potatoes, I stopped eating it.
Pretty much every diner here calls them Home Fries. I've never heard of Potatoes O'Brien. I wonder if it's a regional thing?
Again, it might be a texture thing. All the ingredients are diced & remain chunky. Not wonderfully soft & creamy, then finding hidden bits of stuff in it.
I normally don't like my foods touching each other on a plate. And I will not eat peas that have been covered with mashed potatoes either.