People usually do not put too much money into their pet products. They replace them every couple of years since they tend to get worn down and ratty. People tend to look for quality in their products, as expected, but not to the point of looking for the highest quality item. They wish for something that will last some years - not a lifetime thing. People tend to lean to something that is a prettier color, but when it comes to a dog that is a home dog, people would pick their favorite color of the options - but not base their decision on which collar to get based on sole appearance. An important part of their decision is how the item would fit the dog. Dogs have many different shapes and sizes, so sizing that fits all dogs is complicated.
People usually tend to either go to the store or use the internet to buy things. People who are worried about sizing would likely go to the store to judge it in person.
People believe they have made a good purchase based on the sizing on the dog and the length of time it takes until the product becomes ratty.