Maybe because by and large, hotels have a hard time getting around being inspected. So there is no need for the average consumer to spend the time to do the research so they can say "yep, government regulators are doing a good job!"

As with most regulations, it drives up the cost a bit for the end user, but it's worthwhile - and when done properly, invisible to the consumer.

Because they don't need to, because it's mandatory for hotels.