Why destroy Laketown's bridge?

[Rikae]

Originally Posted by The Sixth Wizard

I'd think that Smaug wouldn't want to land on the walkways around Laketown because of their possible flimsiness and the likelihood of him falling in or touching the water. At least he knew that the bridge could hold heavy objects that were carted across every day...

He probably could also maneuver much more carefully on foot than he could in landing - so, land on solid ground and walk across the bridge.