To be fair, composting toilets do require some attention to detail, and we all know that there are folks out there that can't manage that. I suspect that's what is often on the mind of the PTB. And of course, never discount plain old bureaucratic inertia. Nevertheless, it borders on criminal to use potable drinking water to flush the icky-poo away, IMNSHO.
Here's my favorite bare bones system - Very easy to implement. (Obviously not suitable for frequent travellers, although I use (something like) this system at my summer digs.)
Wow! The last fellow to use that outhouse must have eaten a bunch of bean burritos for it to be blown off the foundation like that. It's a 2-holer so you know there had to be some blowback. I bet he won't do that again.Retired outhouse, Lake Valley, NM.
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BTW, well worth a visit. It, and the Lake Valley National Scenic Byway, would make a semi-ambitious but comfortable half-day trip from either Elephant Butte or Hatch, NM. It's a real ghost town (no ice cream shoppes). Not a lot else around there except a whole lot of God's country. The site host gig (it's day use only, but I think there is someone onsite 24-7) could be fun if you reeeally like solitude. They have weird closure days so check before going.