Some times it does not make sense to associate a time component to a date, just because it happens on a day, not at a certain time.

For example, in a lot of countries, Labor Day is on May 1, Christmas on Dec 25. These do not happen at a certain time, and there is no timezone to be associated with these events.

If I'm requesting some user's birthday, I'm going to store it as a date. I don't have a time component. I don't know the time zone. In some cases, dates are just dates ...