In an apple, making it seedless wouldn't change the overall shape much- the different texture that signifies the core would still be there- and people have been trained to not eat the 'core'. In cherries, it's already a expensive to pick such small fruits, removing the stone would make them even smaller, increasing the cost to harvest.

I adore UFO's (stoneless peaches) and would absolutely love to have a stoneless cherry tree in my yard! Not commercially viable but a fun oddball plant for gardeners.