Because a solar panel's efficiency is proportional to the cosine of the angle to the sun, you actually don't gain that much performance from east-west tracking

Because a solar panel's efficiency is proportional to the cosine of the angle to the sun, you actually don't gain that much performance from east-west tracking -- it's maybe 20-30% better. These days, the panels themselves are cheap enough that it makes sense to just buy more of them, instead of adding enough motors and mechanical components to move panels that weigh millions of pounds in aggregate.