They forgot the biggest downside: when you REALLY need to stop RIGHT NOW, you're not thinking about what kind of brakes you have. You're running on instinct, and that instinct probably says "do a grabby motion with your hands", but that doesn't work, and you don't brake on time.
Source: I have a bike with one coaster brake and one normal one. Have never intentionally used the coaster brake, have used it unintentionally many times.
Source: I have a bike with one coaster brake and one normal one. Have never intentionally used the coaster brake, have used it unintentionally many times.