I suspect this is another legacy of the Four Thirds system. All but the cheapest Olympus lenses were sealed there. It was great. The system also had lens hoods with every lens and no compromises optical quality.
But that system pretty much died. Now they are doing things differently (including the
omission of lens hoods on the premium lenses). It looks like whatever they are doing now is working better than what came before, since they are selling a lot. I can't really blame them, well except for the stupid lens hood thing.