It's marketing driven; we all know that. Unfortunately, it works. If it didn't, they would not do it. I've seen data that shows pushing seasons ahead creates more spending opportunities that are, in fact, realized in sales growth.
Don't want this to happen? Tell everyone you know to quite buying stuff ahead of season.
In my little corner of the world, this is my preference ...
Memorial Day sales no earlier than two weeks prior
July 4th sales (fireworks, etc) would be no earlier than mid-June
Back to School sales no earlier than July. (I actually saw a back-to-school local TV ad and my kids had not finished the semester yet for summer in early June!)
Labor Day sales would be no earlier than mid-August
Halloween stuff starts on Oct 1
Thanksgiving stuff starts right after Halloween
Christmas stuff starts the day after Thanksgiving
New Years stuff the day after Christmas.
I abhor when they leap-frog the Holidays ahead for the purposes of sales, but fiscal returns do pay it back, so they bend the rules to make a buck. I hate it, but I cannot seem to stop it.
(PS - feel free insert your own fav holiday and other stuff in there as well ...)