It definitely comes down to individual susceptiblity. In most cases, your body will get rid of half of the lead that you ingest. The other half is absorbed into the bone marrow. How much lead your body gets rid of depends largely on your diet. Lead takes the place of iron in the body because your body can't tell the difference between the two. If you take in more lead than iron, chances are, you'll have a high blood lead count. Iron as well as calcium will help rid the body of up to 50% of lead.
I know when I was a kid, we always had a protein on our plate as well as a vegetable. Nowadays, kids eat a bag of Doritos and a Mountain Dew for dinner. That's why lead poisoning is a bigger problem today than it was years ago.
All of us have lead in our bodies, but for most of us, it's such a small amount it doesn't effect us.
As far as lead pipes are concerned, most older housing stock still have lead pipes going into their homes from the main. Over the years, the inside of the pipes get calcified from the minerals in the water, thus forming a " protective barrier".
And for all the old timers who say they chewed on sinkers and whatever else......there were definitely side affects to that. It was just too minimal to even notice.