You know, just because it's in an RFC doesn't mean it's actually practical. 'home.arpa' is significantly worse than every other option.

If you actually think it's a trivial affair to change a well-established default with more than 20 years of history that is, on top of all other difficulties that such a change typically encompasses, used to identify and name things, I hereby beg you to never design or provide any kind of infrastructure.

An update wouldn't change all the existing configurations.