I was thinking the same thing. Practically, the only place for me to empty out is via the roaming pump out boat.We have a pump out boat and I can't see him waiting around for all that BS. I'd fill his tank!
Yes, there is a pump out barge. But it's quite tricky to dock to, and if you do manage it usually either the manual pump mechanism or the adapter are broken. Or both.
There's a public pump station in the next harbor. But you have to hope someone is around to get it turned on. And then there's no water for rinsing.