Rain boots are probably a necessity for some folks, but in these work-from-home days, they get bonus points for simply decreasing the friction to going outside during inclement weather. In Scandinavia there's a saying "there's no bad weather, only bad clothing."
I walk around in wet weather a lot, and had previously just accepted that my (waterproof) sneakers would just get dirty and the bottom of my pants would be flecked with little bits of mud — rain boots to the rescue! They live by the door during the rainy season so I can slip them on after gauging the conditions outside. These ones from Target are cheap and comfortable and way less of a thing than all the fancy heavy-duty boots I tried on at REI.