The use of lead alloys in telecom cables started in the 1880s and the industry began to phase out placement of new lead-sheathed cables in the 1950s after developing a new type of sheathing," the trade group’s website said. “Some of these cables still provide customer voice and data services, including connecting 911 service, fire alarms, and other central monitoring stations.”

Sounds about right. So they did stop using it when the negative effects of lead started being more well-known. You know what happens when they try to remove that cable in favor of fiber? You get people who whine that the telcos are getting rid of landline copper connections.