The only purpose of this law is to prevent votes from being pilfered by other options (libertarians taking votes from republicans and potentially causing a win for democrats). Now, instead of actually providing a better product, the parties decide to make sure that the pilfering cannot occur. They utilize the system to avoid making improvements.
Unfortunately, humanity is ****ing retarded, so the people who are dissatisfied with the options (most people) will still eat the dogfood they've been fed because they buy into the line of bull**** about "the lesser of two evils". Instead of demanding that the market be allowed to decide unimpeded, people simply surrender to the dichotomy.