I wouldn't want to use one of those for any of my loved ones. Too much like shoving the casket into the luggage compartment on a Greyhound bus or airliner. Not at all dignified.
One of the most dignified funerals I can recall involved a man who carried his wife's casket from SLC to Rochester in the cargo compartment of their converted MCI coach. He also flew a NY Licensed FD to SLC to accompany the body and deal with legal formalities that might pop up.
Looking back at the event, it was among the most dignified funerals I can recall. That coach was their home for a few years, and the 32 hour trip satisfied what both desired.
Pomp is not a measure of dignity, and Dollars expended aren't either. Many good men have taken their last ride in the back of a pickup in farm country accompanied by family and neighbors. Would you suggest that is undignified? Need and circumstance should and often do drive spending.
I can trace hearse/buses back to the 30s when they came to market to fill what was thought to be a need to transport the family to the then developing cemetery no longer in the city church yard. Most people in that time didn't own cars, so transport was a problem. The bus+ was designed to fill that need, and appears to have flopped as a marketed product.
Airstream's reintroduction when they did it in an era of contrived fuel shortages and crashing RV sales proved to be a solution in search of a need, and it too appears to have been a flop.
Your opinion may vary from mine. That's fine by me.