The constantly changing toothbrush
You have to be pretty confident (and as it turns out, also wrong) that toothbrush handle shapes are not going to significantly change over the lifetime of your bathroom to install a ceramic toothbrush holder directly into the wall!
My current toothbrush barely fits, but my previous one did not fit at all and had to lay across the top. Do you think your toothbrush would fit?
Trust me, they would not continue to make all of these gimmicks if they were not being purchased by a large majority of us across the nation.