I've never heard a compelling reason for seating heads.
One push on the drum head after you finger tighten all of the tension rods is a good idea;
because, sometimes the drum head ring is not fully seated into the hoop. And the push will force it up into the drum hoop.
As an alternative you could seat the head into the hoop before you mount it on the drum just to make sure the head is going to fit easily into the hoop.