From what I’ve seen, most urban benches are bolted down—but that doesn’t mean they never disappear. A standard city bench is heavy and awkward to move, and in a busy plaza or transit stop it’s usually anchored with bolts into concrete footings or paving. In those high-visibility spots, casual theft is pretty rare because removing one takes time, tools, and noise.
That said, benches do get stolen or stripped for scrap, especially when metal prices climb or the bench is in an isolated park, trailhead, or underlit street corner. Cast iron, steel, and aluminum are the main targets because they can be sold by weight. Wood, composite, and recycled plastic benches are much less attractive to thieves.
To reduce the risk, many cities now use tamper-resistant or one-way security bolts, weld the frame to embedded plates, or sink the legs directly into concrete. Some add coded markings or even GPS trackers in high-theft areas. So yes, they are usually secured—but no fixture is completely theft-proof if someone is determined and nobody is watching.