Thank you, what a lovely read!
One of the most common (and least visible) attempts at exclusionary design is not to just not build any public seating at all. It's quite common in financial districts, the only people they want in thoe spaces are either walking to work or getting lunch.
And yea, I'd say the most useless of them are mostly there to offer the illusion of a civil, public space. They are perches for the consumer class to drink a coffee on and nothing more. Though, I don't think those spherical ones are even intended for perching. It's just a slightly more visually appealing way of stopping people leaning up against the wall than... with another wall??