Take a pint of fresh-from-the-cow milk and a pint of your typical store-bought pasteurized milk and leave them open on the counter for 2 or 3 days at room temperature. The former will turn into a tart, pleasant smelling mix of curds and whey I'd be willing to taste and possibly consume while the latter will be a smelly, gag-inducing spoiled mess that will almost certainly make you ill.

I've witnessed this first-hand.

Raw milk is loaded with beneficial bacteria that can be naturally culture itself to various ends, more often then not out-competing environmental bad bacterial. Pasteurized milk, devoid of most bacteria to start, will (most often) be overrun by bacteria that will make people ill. I does not surprise me that our "normal" milk is a non-trivial vector of food-borne illness.