They really don't need to be, but jerks sometimes do modify them to be loud even when idling. About five years ago I lived in a neighborhood where some jackass would idle his modified truck every morning at a quarter till 5am. He'd leave around 5am and you could hear the truck for at least a minute as he left the neighborhood and started accelerating hard on the highway. His house was across the street and four doors down and his truck still could be heard through my bedroom window which faced the backyard. I don't know how his next door neighbors tolerated it. This was an exurban area with lots of pickups and even a few commercial vehicles in the neighborhood but he was the only one whose vehicle was loud and it obviously was made that way intentionally.

No; they do not have the loud engines I referred to.