There are plenty of SPD shoes that are fine for walking. I own a few. I even have SPD sandals and SPD running shoes. My favorite SPD shoes for riding are particularly good for hiking in the woods, as they have a goat-hoof-like sole.

I keep slip-on shoes at the office. My SPD commuting shoes are loud on the floor, so I change for that reason. No big deal to me.

I have a compelling reason to prefer SPD which others won't have. I have foot problems, and the cleats help me position my feet properly.