Water Pumps

When I got home last night, I noticed fluid leaking from my vehicle. Upon closer inspection, I could tell it was antifreeze. The leak was originating where the hose from the radiator clamps on to the water pump. My first thought was the hose had a hole. I was confident I could have the problem easily and quickly corrected in the morning. I had a friend come over to inspect the problem. He delivered the verdict: It's your water pump. So I asked, "how and why do water pumps go bad?" He proceeded to inform me they have a hole that is "plugged", and when the plug goes, there is nothing you can do except replace the pump. This sounds highly illogical to me. Why would a water pump have a plugged hole? If the hole has to be plugged, why do you need it at all? I suppose if the statement is true, then it is all about money. I can hear the 'water pump engineers': "Hey Joe, let's put a hole in this thing that has to be plugged. Then when the plug gets old and falls out, consumers will have to buy an new pump. That way, we have job security. Sure Bob, that sounds like a great idea."
On the other hand, maybe my friend knows nothing about the construction of water pumps. Maybe he was just pulling my leg. When it was all said and done, I spent 26 dollars on a water pump, 8 dollars on some antifreeze, and paid him 25 dollars to replace the pump. Not too bad I think.