Old benches in parks used to be put there for people to sit together, so that more than 2 or 3 persons could use them at the same time. But then, people could also sleep on them, cause their average length was only a little shorter than a real bed.
In the past 10 years, there is a tendency to install benches with handles in parks, at bus and train stations. The space between the handles is enough for only one person, so people sitting together on the bench are separated by handles. This way, a body of an adult person could not fit to lay down. Because the presence of homeless people in city centres is less and less tolerated, this became a very popular solution.
Sometimes the sitting places are not on the same height, which also makes it unpleasant to sleep.
There are many other designs that prevent sleeping, or even comfortable sitting in public space. Benches with curved surfaces, thin sitting stripes, our of cold metal, with an unusual angle… are offering a place to sit down, but not for long!