The center console runs all the way into the back seats. My friend asked me why. I told him it was for structural integrity to make up for the suicide doors.
Then I realized, I've always just assumed this is the answer.

Is this really why?

 

well driveshaft and tranny is in it, the car is low so it has to go somewhere.... It does make the car stronger too.

 

Back in ancient times when all cars were Rear Wheel Drive, they all had the center tunnel.

 

"Making the car stronger" isn't really true, since that tunnel is standard in most RWD cars. The difference is the RX-8's passenger seating is so low that the tunnel is more pronounced than on other cars.
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PORNSTARS GERMAN

 

Because it looks FREAKIN' cool!

 

The hump and console is higher than a traditional read drive vehicle because the rotary shaft is in the center of the engine, instead of at the bottom. So the transmission and drive shaft are higher, especially for a low car like the 8.

The Chevy Vega was originally designed for the rotary, so had a high hump. When GM dropped the rotary project they were able to lower the hump.