Flex

One benefit from the institution of a regular shemitta year is the ease with which creative destruction can occur. 

During shemitta the established power structure is weakened and the possibility for innovation is enhanced. The year after shemitta would likely be a year when lots of new ideas would be tried out and some of them would be implemented. The shemitta year is a year of general subsidy of creative novelty. With a shemitta system in place it is easier to imagine people changing their minds about how things should work. 

Shemitta puts a certain measure of flex into the social structure so that it can bend with the wind and bow under heavy loads without having to snap in brittle rigidity. Shemitta is not just the last year of a six year production cycle, it is also the first year of a six year implementation cycle.