The main thing ironically is using less power than a phone to do the same things. Especially in really long rides, having the bike computer do all the tracking and show maps, etc. ensures my phone won’t be completely dead. The bike computer also won’t overheat in direct sunlight and the screen is matte and readable without backlighting unlike a phone. It also weighs less than a phone if you are a gram weenie and willing to leave your phone at home.
Separately, not all phones support ant (especially iPhones). Ant is a special low power protocol that other bike devices like power meters, cadence sensors, and heart rate monitors use. Especially higher end devices do everything they can to weigh as little as possible and still have a years long battery life and using ant is one of those methods. Bike computers all support ant and have better compatibility with all these other components. The bike computer will also usually support more simultaneous devices than a phone. Especially cheaper phones tend to have issues streaming data from 4-5 devices at the same time
Finally, bike computers do actually do things regular phones don’t. For example the new wahoo bike computer has a built in wind speed sensor that tracks when you are biking with or against the wind and adds that data to all the power and calorie calculations
That all said, I rode for years just using Strava and android health to track most things. The bike computer has made all that better but it is definitely an optional accessory that you probably don’t need if you are a casual rider
The main thing ironically is using less power than a phone to do the same things. Especially in really long rides, having the bike computer do all the tracking and show maps, etc. ensures my phone won’t be completely dead. The bike computer also won’t overheat in direct sunlight and the screen is matte and readable without backlighting unlike a phone. It also weighs less than a phone if you are a gram weenie and willing to leave your phone at home.
Separately, not all phones support ant (especially iPhones). Ant is a special low power protocol that other bike devices like power meters, cadence sensors, and heart rate monitors use. Especially higher end devices do everything they can to weigh as little as possible and still have a years long battery life and using ant is one of those methods. Bike computers all support ant and have better compatibility with all these other components. The bike computer will also usually support more simultaneous devices than a phone. Especially cheaper phones tend to have issues streaming data from 4-5 devices at the same time
Finally, bike computers do actually do things regular phones don’t. For example the new wahoo bike computer has a built in wind speed sensor that tracks when you are biking with or against the wind and adds that data to all the power and calorie calculations
That all said, I rode for years just using Strava and android health to track most things. The bike computer has made all that better but it is definitely an optional accessory that you probably don’t need if you are a casual rider