Naa Doug, no doors are more practical! Like a WWII Jeep!
"The new Mazda 6 with the optional "no doors" package..."
Sliding doors are quite un-practical untill they are open. With a sliding door you have the problem of the exterior and interior tracks. On a car like the RX-8, a track on the side would really mess it up, HARD
!. Also, they absolutely have to be only the back doors of a car with more than 1 door on one side. Otherwise you'd have doors hitting each other, or the tracks would have to be on the roof and crap. Impossible to manufacture in mass production.
Even on vans, sliding doors can easily hurt people. Parking downhill, with the door held open, you let og of that door and it's gonna go pretty damn fast forward and slam shut. Put a body part in there, and the person will either be
mostly in the vehicle or out of the vehicle.
There's also those electric sliding doors. Sure it works great when the electrics work, but when they don't, like if the battery dies or something bad happens, the door weighs more and becomes harder to slide.
The only major problem with standard doors is at angles. And most parking lots don't have enough of an angle to cause problems. Sure you can get your finger stuck in the door(I know I have...my mom's old '80 Corrola 2 door hatch...no door frame on the window on the door or on the side of the car, so my thumb was smashed between 2 pieces of glass...worse yet, it was at my elem. school, and I was locking the door for my mom(luckily she walked out with me and was able to help), so the door didn't close all the way, but it was locked with my thumb in there. Hurt!), but on most parking lots the door closes with the force you put on it to close, not usually with gravity, so it's not going to be a horrific injury.
You can get hurt with any door...
Well, a doggy door might work....naa!!