It makes the tub taller than it is deep by a little bit and doesn't look as nice are the only reason I can think of. A little bit of splashed water just isn't a

It makes the tub taller than it is deep by a little bit and doesn't look as nice are the only reason I can think of. A little bit of splashed water just isn't a big deal in most wet bathroom setups. They could also just put a drain right off the side of the tub.