Another schoolboy error

Why the hell do they put metal railings on the sides of pavements? I'm referring to a strip of metal that is attached to the road-facing edge of a pavement. It's solid steel, it's slippery, and it's responsible for me doing a proper comedy-slapstick slip and stumble.

I'm amazingly athletic enough to have kept myself upright (scoff), but not before people saw something that'd probably keep them laughing for the rest of the week.

I'd have laughed at me anyway.