If the motor drive on the Elan II sounds a bit different from that on the Elan and also seems slightly slower, that's because it is. The Elan II uses a single drive motor to transport the film, move the mirror and charge the shutter. The older Elan used two motors, one for the film transport and one to move the mirror and charge the shutter.
Economy is the best guess.
Presumably Canon were trying to keep the cost of the camera down. The major downside is a drop in film transport rate from around 3 fps to around 2.5 fps. Most of the time this isn't a big deal. The old 10s, RT and 630 also were rated at 5fps. These drive speeds are for one shot focus.