Some parables are allegories, for instance, the parable of the sower is an allegory: the seed is the word of God, the thorns are worries and greed, etc. But most parables are not allegories but simply stories to illustrate one point. It's dangerous to get our doctrine from parables; they can be twisted to say all sorts of things. We need to get our doctrine from clear scriptures that lay it out; then if a parable illustrates that, fine.
The parable of the widow with the unrighteous judge in Lk.18:1-8. This story illustrates one lesson: boldness in prayer. If we draw it into an allegory, what do we have?
All sorts of violence happens to the meanings: God is reluctant to protect the rights of widows, prayer "bothers" Him, etc.
The parable of the unrighteous steward in Lk.16:1-9. What is the point of the parable? Is it an allegory?
The steward is commended for only one thing, his shrewdness in using what he had to prepare for a time when he wouldn't have it. But he is not commended for his unethical behavior in cheating his master.