So why fly circuits? Because downwind joins are the norm and overhead full circuit joins very frequent, and sometimes circuit practice or currency requirements makes 'em unavoidable. Just be kind to your engine when doing them though!
As for an aeroplane that ices up the carb as soon as power is reduced. I think I would swop it for something less scary but I can certainly see why one would want to hug the airfield in those circumstances.
Mike