More customers are dropping cable TV as they turn toward streaming services like Netflix Inc., a fundamental shift in consumer behavior that was on display this week in painful earnings reports from cable and telecommunications companies.

Charter Communications Inc., the third-largest U.S. pay-TV provider by subscribers, said Friday it lost 122,000 video customers in the first quarter, a far worse outcome than the roughly 40,000 subscriber losses Wall Street analysts expected. In the year-earlier period, Charter lost 100,000...