>>kjkjad+(OP)
Port-a-potties require frequent emptying and other kinds of maintenance. Other kinds of dry toilets are under development which would address this issue in a variety of ways (e.g. composting toilets) and be applicable to all sorts of interesting scenarios (e.g. remote places in the developing world, where proper disposal of human excreta is a severe public health concern) but overall they're not yet ready for prime time.