Yes, some mappers can replace the default hitsounds accordingly, however, that doesn't mean it's possible for all other mappers. If so, there would be additional burden for mappers to satisfy those who'd like to disable hitsounds, which would be a pain as mappers endeavor to provide best hitsound experience for players and some are even begging them not to disable hitsounds. So it is recommended that players put on the hitsounds, not mappers cater to players insisting on their own hitsounds in the skin.
And also, if such a rule/guideline existed, there would be too many ambiguous cases and exceptions due to various use of hitsounds, and thus it would work terribly to the extent of execution, as you even need to take the variety of players' skin into consideration, which goes too far.
And also, if such a rule/guideline existed, there would be too many ambiguous cases and exceptions due to various use of hitsounds, and thus it would work terribly to the extent of execution, as you even need to take the variety of players' skin into consideration, which goes too far.