Decency is subjective, and there are enough outliers from 'average decency' that it's important to formally state what is, and isn't acceptable for a community

Decency is subjective, and there are enough outliers from 'average decency' that it's important to formally state what is, and isn't acceptable for a community of people. Society has laws, and any subset of society that forms into a community will draw tighter boundaries around what and how they define whats acceptable within their community. Then add the lens that within any community there is always going to be power differentials where some people in the community have more power than others, by position, contribution, or just stupid historical reasons like "wealthy and has lots of free time". Declaring how power in the community works (i.e. who is in charge, who has decisionmaking, who has commit access) also needs to be written down. So, anybody who's ever in a position to potentially be the target of poor behavior is much more likely to feel like the community has their back if something bad goes down, because its all written down about whats going to happen if somebody does behave out of bounds.