Cost, it's mechanically simpler to produce cylindrical wallpaper and baking foil, same for batteries.
Strength, companies like nissan actually use strong metal cans to store and cool their prismatics, and a bike with cylinders may resist a fall better.
Cooling, cylinders provide some expansion space and some cooling. Cylinders with cap-cooling last longer than cylinders will external cooling because the cooling diffuses through all the layers of the battery.
Easier storage and manual labour costs, cylinders are difficult to short circuit due to the tabs being at opposite ends
Size flexibility, cylinders are low priced because they cover many markets, bikes, pc's, shavers, vapes.
They will perhaps do prismatic car cells that are easier than cylinders because of the size constriants, but cylinders are easy to move between robots on conveyer belts, and have 2x types of protection which may eventually have 100% short circuit protection, except for tesla which doesnt have internal battery protection afaik.