I think our very first trip was almost completely dry, but everything after that I have carried some amount of water in the tank.
Mostly because of using the bathroom. Once you realize that you are carrying your own stuff around, you're much more comfortable. I've pulled off the side of the road, rest areas, gas stations, you name it, to use the facilities or for the girls to use them. They much prefer it.
We have an under-sink filter, so drinking water will come from it as well, and I usually carry 12 or so bottles of water in the fridge in case we need them for something. The girls get extra filtering since I bought them a couple of Brita filtering water bottles the last time we went to Disney. Very convenient and kills the 'Florida' taste in the water. By the time they drink water that has been in the RV it has been triple-filtered. Camco filter on the hose, under sink filter, and bottle filter.
Here lately I've been loading about 20-30 out of 40 gallons in the tank. When I get home, I'll use whatever is left for cleaning up the bathroom and kitchen, drain the rest, and then refill from the hose (city water). In my mind, the small amount of chlorine in that water should help keep the tank sanitary.
I don't carry any large totes of water. That is something I might think about when we go longer with our trips and plan our SD trip for 2025.