Buzz said:
The engineering cost to design the door with opening glass would have been minimal.
I would guess that this was a compromise to keep the manufacturing costs down.
Not sure where you get the idea that the cost to engineer would be "minimal"...
A sealed, flush-mounted glass panel is easier to integrate and has a lot less effect on aero- and aquadynamics. First of all, making it openable -- whether it retracts into the door or flips up like a hatchback -- would reduce the visible framing size of the opening, due to inherent design needs. This, in turn would require a complete redesign of the rear door -- the RAV4's wiper has always been mounted through the glass and the panel stretches across the entire width of the rear door, edge to edge.
A retracting window, like a door window, requires a certain amount of space in the door cavity to house a completely lowered glass panel, an electrical motor, as well as all the mechanical parts necessary to motivate the glass up and down and still provide power to the defrosting grid and stay clear of the rear wiper blade (or mount it on the glass). In the meantime, it still has to be weatherproof and be able to withstand a lifetime of a large and hefty rear door slamming shut, no matter what position the window is in. With a retracting window, I'd expect that the spare tire would no longer be able to reside on the rear door, owing to the ease of catastrophic damage in even the slightest accident and the need for additional structural framing and reinforcement.
A hatch type of window needs room for exposed or hidden hinges and gas assist struts and locking mechanisms. An all-glass design leaves exposed mounting rivets and must also contend with the rear wiper, door slamming, additional weatherproofing difficulties and wind noise.