Seagate Accuses Cornice of Patent Infringement
Without some protection of having your work stolen ( and future income derived from it ) from you, why bother at all?
Reverse engineering from the commercial product is not always so easy as you make it. It's not simply a matter of taking the product off the shelf and having factories pop up like mushrooms.
A company might be confident that reverse engineering would be too expensive for its competitors, or that it would take long enough to make it irrelevant...
It might well be that in a market that evolves quick enough, patents do more to slow and even prevent innovation that to encourage it.