Maybe you've never used a modern PP. They have sealed holding tanks, fit into a canvas shopping bag, and tote just fine.
Hey, if you're perfectly happy toting a canvas shopping bag of human waste on a regular basis, be my guest.
But if that was the case, would you have started this thread in the first place?
The honest-to-neptune old school jabsco head on my boat is over 15 years old. In the five years we have had her, our total maintenance has been...
No hoses to replace, no gaskets to fix, no valves to rebuild, even though our winterization has occasionally been suspect and the boat is stored on the hard uncovered in winter.
A little baby oil in the bowl from time to time and a spoonful of sugar once a month or so takes care of any odor issues.
When you hear about those who have had major issues with marine heads, ask them why. Chances are you will discover that somebody didn't bother to read the freakin' instructions- didn't flush it properly, disposed of something they shouldn't, or inherited a problem, and the head was a symptom of a great deal of other deferred maintenance or ill maintained aspects of the boat.
Meanwhile, friends of ours who bought a powerboat with a porta-potti head couldn't figure out why the underside of the aft cabin mattress was always wet and stinky- turns out there was a crack in the holding tank from a PO's overzealous fastening of hold down brackets, leading to leakage whenever the boat planed with the tank more than 1/4 full.the leaking liquid would run back under the aft bulkhead into the aft cabin to be absorbed by the mattress. When the boat came off plane, the leak stopped, making it a difficult problem to trace...for weeks.
When they finally discovered the cause behind the sodden aft cabin bedding their daughter wigged right the hell out and refused to sleep in "the cave" any longer, they sold the boat and divorced shortly thereafter. Not saying the last two events were connected but...