You might not really notice it, but there is a lot of chaos happening in airports all the time. However, decades of organizing and optimizing foot traffic, boarding, and many, many other processes that happen in an airport has made it possible for the various teams of staff on the premises to make sure order is kept.
And, so, if you think nobody’s going to notice you sitting down in first class, all nonchalant without actually having a ticket or hoping you’d get a seat upgrade just like that—you have another thing coming.