Well, they have. Cars are enormously better than they were twenty years ago. The controls are far more usable and standardised. The engine delivers power more smoothly over a broader range of speeds, while emitting less pollution and making less noise. Accidents are less likely due to better handling and performance, and when they happen they're much less hazardous to the occupants and even to pedestrians. Cars have sensible user interfaces for opening doors and turning the lights off. You can buy cars for carrying a passing fling or an extended family, and you can buy them as cheap accessories or as durables.
If the computer industry had evolved computers in the way it thinks the car industry evolves cars, we would all be using home computers that could only add numbers between 0 and 255, but could do so on four concurrent streams at a rate of two billion numbers a second each. They'd display fabulously crisp images on your HDTV using 8, or maybe 16 colors chosen to include cyan and magenta. The computers would forget everything between each use, including you, and you'd have to type epic BASIC programs or insert several USB sticks in the correct order to tell them what to do. Computers would differ by having rigid keys or rubber keys, but they'd all run for 1000 minutes on four AA alkaline batteries and nobody would pay more than $25 for them.