I fear the indignity of simply carrying around one's feculence in a bag would become irksome. And what if one suffered gastric problems? Would the thing just keep filling up?
Ideally, one ought to be able to hook oneself up to a pipe in the wall once a day that simply takes all the unpleasantness away and means one doesn't have to worry about it for another 24 hours. It seems ludicrous to me that human progress has not reached this point.