Victor Menaldo explains:

[L]egislatures, along with political parties and courts, allow a dictatorship to formally institutionalize their political power by defining who qualifies as a regime insider and who does not, what political insiders’ rights are, and what tools they can avail to defend their rights and pursue their interests. Along these lines, legislatures allow a dictator to do two important things. First, usher in a stable distributional arrangement, in terms of who will benefit from rents produced by the coercive power of the state and its politicized regulation of the economy. Second, help a dictator credibly commit to protecting the property rights and vital interests of regime insiders—not only in the immediate present but in the uncertain future, and even when the identity of key individuals who helped launched the regime into existence has changed.