The correct answer is - They just haven't gotten those salts to those people who need it.
Explanation:
The rehydration salts fail in India to solve the issue of diarrhea due to various reasons. Some of such reasons are the willpower of government and also it only provided to the places that are accessible and not reached the part of the last mile of the country.
Due to this reason, even the majority part of the nation got covered and solved the dehydration problem but fail in reaching the people who need it in places that are accessible.