It's one of those "unwritten" rules from the aristocrats of days gone by! It was only "proper" to wear from (some say Easter) Memorial Day through Labor Day and then to put them away. It was as important as which fork to use for each course, where the proper setting for a napkin should be, etc.

Now we are talking about whites - pure whites - it is acceptable to wear "winter white" during the "colder seasons" - but the pure whites were always put away until the following year.

Back in the days of things being "socially acceptable" and what a "proper" gentleman or lady would do.

I still stick to it myself - old habits and beliefs are hard to break.