The donated handmade wooden benches are not ADA compliant so the city is forcing the builder to remove them. So having literally nothing is the alternative. Also the city says the builder can put the benches in their parks, but wouldn’t that also need to be ADA compliant?
There are tons of other mobility issues people have short of wheelchairs like mobility scooters, crutches, those scooter like things for leg injuries. Or they might just like to park next to the bench and hang out with someone they know, like a regilar person.
But mostly because when the bench is mounted to the concrete it gives the bench a solid base so that if someone is off balance and leans really hard against the bench, it won’t topple over. Think elderly people, or people with balance issues.