Why does Prettier turn trailingComma on?

The trailingCommas option is based on esnext when Prettier is turned on. But why is this the case? Neither XO nor Prettier allow trailingComma by default.

https://prettier.io/docs/en/options.html#trailing-commas

[sindresorhus]

The trailing comma makes git diff more readable and allow to find which git commit modified which property in an array or object more accurately, so it might make sense to enable it when esnext is true.

I’m still not personally sold on trailing commas and it would be a pretty controversial change. I kinda agree with the code manipulation argument, but it’s never bothered me very much. The Git argument is just trying to fix the problem in the wrong place. The solution there is better Git diffs.

[kevva]

Currently, it’s enabled when esnext is true, disabled when it’s false

Sorry, I meant the other way around. But the question still stands, why enable it at all for prettier when it’s always false in xo?