I understand that they want more information, but they don't need it. Ask your clients how they evaluate the performance of offline ads. Those same analytical techniques work online as well.

I think super-precise attribution would actually kill the advertising industry. The uncertainty is what allows ad-buyers to purchase spots well below their value. The uncertainty is what leads to money being spread around and supporting the most things.

It's a little like insurance. If insurance companies could precisely target rates, you would end up paying basically exactly what your health care costs are and maybe a little more. Insurance works because of uncertainty and large pools of customers.