You make a good point
You're most likely right that it has been there for a long time. My understanding is that testing is a lot more available than it used to be. Even individuals can purchase test kits and test for lead.
Why do they even still put lead in paint? They know what it does.
On the other hand, I still remember taking some of my cat food back to the store. I don't think that was anyone else's responsibility other than China's.
We just have to be wary of damn near everything we ingest or use these days. It's getting a lot more complicated being a human these days.