As a five year old I would say your explaination is correct it is a new eco system.

I have very little faith in the planning of our infranstucture sewage, roads and such. I love how no gets the memo that they are repaving a road because the minute the asphalt is dry someone is there to dig it up. and once that patch is done sure enough someone else will want to cut the street open. So why would a drain have any forethought or planning.

Someone decided it needed to be there and they put it in! o explain something means there is underlying logic. But the way I see it there is none!