While there are exceptions and some isotopes of lead are also radioactive, lead is the most common final product of radioactive decay. This is because lead has a high number of stable isotopes, making it a common endpoint for various decay chains.

Here's why:

* Radioactive decay seeks stability: Radioactive decay occurs because unstable isotopes release energy to become more stable.

* Alpha and beta decay: Many radioactive decay chains involve a combination of alpha and beta decays, which change the atomic number (number of protons) and mass number (number of protons + neutrons) of the atom.

* Lead's stable isotopes: Lead has four stable isotopes (204Pb, 206Pb, 207Pb, and 208Pb), making it a common "sink" for decay processes.

It's important to note that while lead is a common final product, some radioactive isotopes decay into other elements, like bismuth or polonium, which then undergo further decay to reach stability.