They are designed to allow you to sit but not get too cozy. And that is intentional. The concept stems from a school of thought that goes by many names, but today we'll use "defensive design."

它們是被設計來讓你坐的，但不會坐得太舒適，那是有目的的。這個概念源自於一個擁有不同稱呼的學術思維，但今日我們稱之「保護性設計」。