For whoever has, to him will be given, and he will have abundance, but whoever doesn't have, from him will be taken away even that which he has. Therefore I speak to them in parables, because seeing they don't see, and hearing, they don't hear, neither do they understand. The idea is that long inattentiveness to previous revelation has brought darkness to the eyes of many listeners. To them, the parables of Yeshua create only a greater fog. They are part of HaShem's Word.
Parables are both mirrors and windows.
As mirrors they reveal our lives and help us to see life and HaShem. Study each in its context. Draw out the main truth of the parable teachings. Look for the doctrine illustrated in the parable.