'Halloween' started the slasher genre. John Carpenter made the perfect character in Michael Myers. Emotionless, faceless, and unstoppable. He doesn't fear repercussions, especially legal ones. He'll stab anyone in his way, gte arrested, and escape before the cruiser hits the freeway. It spawned dozens if not hundreds of other movies, most of which suck, but think about 'Scream.' That movie couldn't exist without 'Halloween.' Watch how you speak on John Carpenter's name.
After many sequels, it seems like a poor name choice. "When should we release the next one? June?" / "Halloween in June? Nah." It would sound silly. Not that you even need to release it any other month. A new 'Halloween' movie around Halloween time spells money. The letters M, O, N, E, Y spell money too, but no one has ever bought a lake house using letters, so who cares.