As has been said, it isn't acceptable.
_No_ level of lead is safe and_no_ level of lead is acceptable. That's a statement from CDC, WHO, or any other 3 letter agency you could ask.
Why is it still "used". Often, the difference is in percentage of lead in products when it's intentional vs not (probably obvious). The part that may be less known is how difficult it is to ensure that steel or other metals don't have Working in characterization of materials _can be_ difficult. I have had 3 different pieces of equipment give 10% X, 50%X, and 80% X all for exactly the same batch of the same material.
However, lead is far more established in it's characterization in metals, so _given enough care and money_ these problems don't really occur.
This company, and many others, aren't going to check - that's the government's job to worry about the safety and health of the public, and protect them if a company makes an unknowingly harmful product. The government meanwhile does not have the funding, personnel, or time to tackle such a monumental task.
This is why it takes so long to find bad products like this - it's typically on the shoulders of curious individuals.
To recap, this _should be_ a solved issue (also lead needs to come out of GA, as it has been shown to be possible for decades, and actually _harms_ the engines of small planes), but as it often is, harming people to save money spells success in our world.