I bought a cable with a preposition 65 notice for lead and lead compounds. This notice isn't found for many other cables but I realize it can be excluded from packaging in areas where not required. Is it that most cords/cables still contain lead but don't have notices, or most today don't have lead?

It's apparently used in flexible pvc products, like wire insulation,  to reduce cracking. As long as you aren't chewing said products, that's California going overboard.