Such a bench is very suitable if a confidential conversation is planned. At least no one will need to subtly hint that the third is superfluous. You can play chess, or discuss something face to face, there is where to put a cup of coffee. In general, there are a lot of advantages. It can even be called somehow in a special way.
You can sit alone and read in the fresh air. It is very convenient if you settle down for a long time and take with you a whole bunch of newspapers. There is where to put the periodic press. An armchair with a built-in table is, of course, a very functional thing, but with one armchair, it would somehow look very sad. And so, someone wants to get hooked, do not drag a stool with you.