If they get what's advertised, that's good business. If the race's information includes that it's certified, it also likely means that race management is not only detailed enough to measure the course, it also has likely made sure other components of the race have been professionally orchestrated. Trail ultramarathons are sometimes the exception. Most ultramarathons understand and accept this dilemma. But road racing is different.
Many events understand the concept.
But the reverse is also true, and this is where runners sometimes fail to realize the power of their dollar. If you attend a road event that's not the distance it was billed, don't go back. And tell your friends not to support the event, either. It was a nice feeling of accomplishment. And even as someone who races infrequently, I would have been disappointed if the course wasn't certified and I later discovered it was short.