Not positive on this, but aren't those full floating drum calipers? Avoids wearing down just the one floating end like most drum brake designs are prone to do?
In practice, I doubt the extra complexity materially reduces maintenance, but no manufacturer adds to build cost unless there is a true cost benefit to the overall car. Manufacturers count things that cost fractions of a cent when designing cars. An extra spring exceeds that, so in this case there must be a financially viable reason behind the design.
The only exception to this penny rule, that the guys I spoke with admit to, is power trains. Seems the engine designers can spend without too much oversight.
One note based on personal experience, make sure you record the spring stack sequence when disassembling. On reassembly, one spring stacked under another part on a post can wreck havoc with auto adjusters and parking brakes.
