Everyone has different ideas about what is and is not acceptable. Brandrup makes a tray that fits in the cupboard to retain the cube, presumably they sell 100s at the usual fabulous price they charge for their kit. Some people actually take up to four dogs with them in the van, whilst they are obviously great company their lavatorial habits are not exactly up to Debretts standards, but acceptable to many regardless.
I have memories of a toilet tent being blown horizontal at the Highlands meet in the spring by a freezing easterly force 6, wild horses would not have dragged my wife into such a place, again whatever floats your boat.