Rim brakes have worked adequately for years, so why do you need disc brakes? Modulation is the answer. Hydraulic disc brakes offer huge amounts of braking force, which you can control with just a single finger, meaning you can adjust how much braking power you are using in a fraction of a second. This lets you fully exploit the grip available from your tyres to bring you to a stop in as quick a time as possible.
When this is combined with thru axles, which securely lock your wheels into the dropouts, the result is outstanding braking and steering, perfect for descending alpine passes or dodging the potholes on the club run.