Two possibilities :

1. They reflect the (existing or latent) oligarchy in an already oligarchic society
   
2. even in a non-oligarchic society, they favour the emergence of an oligarchy.

The essence of democracy is government by consent. This does not require the active involvement of every citizen; and clearly it's too much to ask of most people. Sortition may be asking too much.

_{It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II}