Why, after 3000 years, do we still poop in our drinking water?!

My biggest architectural and urban planning related pet peeve of the year, probably of my entire life thus far, 'til we come up with a more appropriate and less antiquated sewage system. Pooping in our water supply. What's up with that? Western civilisation has been using the same type of sewage system since Roman times, 3000 years ago. Remember the Romans? Buncha old dudes who devised the fabulous notion of building plumbing for public bath houses and drinking water out of lead pipes? And consequently poisoned themselves to death? Arguably one of the primary reasons contributing to the fall of the Roman empire? Yeah, them. Using compostable toilets come to mind, some sort of sewage system along those lines. But, oh geez, compostable would require folks to think about disposing of their own feces. God help us if we have to start thinking about where our shit goes after it leaves our bummocks. God forbid we can't just flush it away. Be rid of it. Vamoose. I don't understand, I really don't.. bears don't shit where they eat, cats don't shit where they eat, raccoons don't shit where they eat, dogs don't shit where they eat, even PIGS don't shit where they eat. I know of no animal that poops where they eat or drink. But humans do. Oh yes they do. Hundreds of thousands of tons of poo per year, millions upon millions of gallons of fecal matter flushed into apparent oblivion only to be sucked right back up, lightly filtered, shaken, stirred, and delivered to your tap, a seemingly crystal clear chlorinated poop smoothie extraordinaire. It's a wonder we're the dominant species on the planet. It boggles the mind. How, after the Black Plague devastated Europe a few hundred years ago - presumably caused by dumping our shit onto the street - by living in our own filth - drinking foul water, bathing in disease and bacteria - for those who bothered to bathe at all - to all of this our solution was to build a complex and expensive system of sprawling pipes and resevoirs to enable ourselves to shit in our own water supply. Absolute genius.