Drainage

When we bought the house the Home Inspector warned us that there was a drainage problem in the rear of the house by the great room. Specifically there was a downspout that drained directly on the the ground into a depression which left standing water against the foundation. there was a broken drain head next to the spout but it was not in use, presumably due to it having over time gotten clogged, or the pipe having caved in at some point. I spent a bit of time contemplating what I would do to resolve the drainage issues before, yesterday, we were hit by a pretty huge rain storm. Today, out of curiosity, I stuck a hose into the Drain head and was surprised when watter started to run out at the street. There seems to be nothing wrong with it. I guess at some point someone simply decided to stop using it and flood the back yard instead. I don't understand.