What Bob said! On our boat also, EVERYONE SITS. I was taught this when I first started doing deliveries several decades ago by an experienced owner/skipper. Simple rationale -- keeps the whole darned head compartment 97% cleaner. Also, when the boat is rolling around or pitching, it's safer.

After a multi day off shore delivery with 3 or 4 guys, the wives meet us at the destination, and we present them with a clean interior. Very good for marriage preservation.
Want another piece of unsolicited advice?! (Not hearing a 'no' over the internet...)
When cruising with friends for a day or longer, have everyone choose/provide their own bowl, cup, and spoon. Iron-clad rule is that they keep these with their personal things and *nothing* is ever left in the sink. Nothing.
They can wash and dry it regularly, or add new comestibles to the dried on crud, but it's their dish. You very soon get used to a clean galley. Whole boat is lots nicer. A sink full of dirty dishes, rattling around as the boat moves, is gross, and it's interesting how no one wants to volunteer to wash 'em, including the owner.
edit: now reads 'bowl' !!