Why do we need smartphones? Blackberry works fine already
Why do we need 100Mb/s internet? 10Mb/s works fine already
Why do we need 24 inch monitors? 19 inch works fine already
Why do we need 3.2GHz laptops? 2.4GHz works fine already
Why do we need better headphones? Stock wired earbuds work fine already
I could go on forever :)
It is great fun to realize that back in the day, when you ended up properly pissed in the pub, the pub owner could simply haul you on top of your horse, which would know the way home and deliver you there.
Now with cars we may even need radar on top of video to get similar results. And I doubt you are allowed to be drunk while your car is helping you home.
...but there's a difference. Op isn't saying "why AI?"
- why do we need supercars, cars are just fine? - why do we need megaphones, phones are just fine?