There are two types of airport terminal seats.
Type One - reasonably comfortable bench that in a pinch (delays, cancellations, acts of god, terrorist activities 10,000 miles away etc.) could be used as a makeshift temporary cot.
Type Two - reasonably comfortable bench when sat down that has been designed, specified to be as impossible to sleep upon as is possible. This usually consists of the addition of many arm rests or metal half hoop dividers at thigh level. To create these requires a conscious decision to do so. Something like this - " I am fully aware that bad things happen occasionally and people will end up stranded for hours and hours and sometimes overnight(s). They will eventually become exhausted and often have children similarly knackered. Regardless, we will not have them sleeping on our benches in our terminal and this is how we will do that."
These are the people I like to meet in dark alleys.