I wonder if this is an American thing that you're all describing?
It would be curious to hear if innkeepers from Europe or other places are having as many "customers with attitudes", especially in regards to the number of people in the room.
Our experience in Central America is that visitors from the US, in general, tend to be more assertive and are more rule breakers than people from other countries and are more likely to expect things to run like they do in the states. But here, when they have traveled thousands of miles, they aren't really trying to sneak an extra person in the rooms.
Locals are the biggest culprit here when trying to put an extra person in the room. Luckily it's not my trigger, I just charge.
Out of other countries, the Italians are the ones that seem to think that kids don't count as extra people.