Clutches in an automatic transmission wear out a because the transmission will “power shift” every time. If you floor it and the thing is revving up to 6k up shifting,then dropping to 4 while your foot is still hamming the gas, that right there was a power shift and it just put a lot of wear on the transmission. Even when you’re just lightly touching the pedals, you’re still touching the gas while it’s shifting.
I know some modern autos when coupled with a drive by wire throttle “rev matches”, and is easier on the clutches. Modern engines will do electronic wizardry (e.g. pull timing) during shifts to lessen the wear on the transmission? An auto trans will typically last quite a long time…I dare say longer than most people will own their cars.
Then there’s dual Clutch transmissions, those clutches basically never wear. Your dual clutch system is more like a rev-matched manual. Two gears are always engaged and it switches from one to the other. There’s no synchro time or synchro grinding. That car will shift in 10 miliseconds and it has continuous power, but my truck with a 4l60e has a looooong upshift time and it’s stressing the clutches that whole time.
Most of it depends on how you drive. Your grandma’s automatic will last forever because she accelerates super slow. My auto transmission will be lucky if it lasts 10 years because every merge onto a highway or freeway is a pedal to the floor clutch burning extravaganza. Automatics really don’t like being loaded down, which is basically what I’m doing when I’m flooring it. If you buy a van or suv and it has an optional towing package, that towing package likely includes an additional cooler for the automatic transmission. Heat is caused in part by the clutches slipping.
To say that clucthes in an automatic trans never wear is absurd.