We see lots of the big rigs up where we go boondocking. They make our 25 ft TT look tiny.
As for the cord, when we started there was none. The few CGs we have used might have a tap or hand pump but some of those were red tagged so we got use to conserving the water. Now 50 gal last us 10 days including showers.
The rest of my family OTOH does nothing but FHUs and even though they love looking at the pictures of where we go, they wont even consider unplugging. They like long hot showers, washing dishes in a full sink of water while running the tap for rinsing and never even thinking of the batteries. To each their own I guess.
So how do you get people to unplug? You have to get them to want too. One buddy of mine only started doing it after he asked me how much our spot cost for 10 days and I said nothing. After discussing the how to, they started out for a weekend, then a week and recently came back after a two week trip without hookups and you would have thought he was a new proud papa he was so pleased with himself. They had just never considered it because they didn't know how or where. They have bigger tanks than we do and more room for solar so I bet next year they will be able to stay out longer than we can.