Save you
money. Reduce sources of faults. Reduce weight. Reduce effort to
repair and maintain. Reduce the number of through-hulls. Meet
legal requirements. Reduce off shore empty out issues. Reduce
pump out effort. Not predict that some people might be annoyed by having to make a choice. Etc. etc
Solution: I assume that this is a night time problem as both toilets might be readily accessible during the day albeit, you're still forced to remember which is which.
So, sleep in the guest bedroom or move the
holding tank across to the ' master'
head.
I guess boats are rarely fully resourced to cater for every individual's taste.