The reason is solely one of cost. The turntables are driven by a two-pole synchronous AC motor, which is a cheap type of motor which will essentially start in a random direction (it actually depens on where in the AC cycle the power is applied initially). It can be used because it doesn’t matter one bit which way the turntable rotates.
That’s one I’d never have guessed. Some brands list it as a feature, and it’s really a cost saving with no benefit to the user? Well, the pitch worked on me.