It is true that every fruit free that does not bear fruit should be cut down, but expecting fruits from a fig tree when it was not the season for figs is not fair. God Himself is the author of seasons.
Surely, Jesus knows well the laws of cause and effect. Why, then, did Jesus curse the tree for failing to deliver on what is clearly out-of-season expectation? Did he act irrationally as a result of hunger? Was he not the one who withstood Satan's temptation to turn stones into bread after a forty days and nights fast?
'In the morning, as he was returning to the city, he was hungry. And seeing a fig tree by the wayside he went to it, and found nothing on it but leaves only. And he said to it, "May no fruit ever come from you again!" And the fig tree withered at once.' (Matt 21 : 18, 19)
A case has been made that he was driving home the point that we needed to be prepared to account for what we are given without notice. But, does this hold true even when the work is in progress?
However, what happened to the tree is instructive. Jesus did not say exactly that the fig tree should die. He said,
" May no fruit ever come from you again!" (Matt 21:19)
I think it translates that for it to never bear fruit again means death. To live, therefore, is to bear fruit, and to not bear fruit is to die.
Because of Jesus' curse of barrenness, the tree ceased to be in the basic condition to live, which fruit bearing condition. God said He will bless whom He chooses and curse whom He will, so we may not fault Jesus' action.
But we have seen that when one loses the capacity to bear fruit, one withers and dies. Really, it doesn't need saying any more that we need to bear fruit to continue living.
You say, 'what if we can't bear fruit?' We can, because we are alive, so the seed is in us. We would be dead already if we could not bear fruit.
Now, to the aspect of this incident which the church belabours. Faith to do anything.
'When the disciples saw it they marvelled, saying, "How did the fig tree wither at once?" And Jesus answered them, "Truely, I say to you, if you have faith and never doubt, you will not only do what has been done to the fig tree, but even if you say to this mountain, ' Be taken up and cast into the sea,' it will be done. And whatever you ask in prayer you will receive, if you have faith."(Matt 21: 20-22)
It is becoming clearer now. With the argument given above still holding true, I say that the fig tree was sacrificed for the underlying reason of Jesus wanting to demonstrate to us how we can accomplish obviously impossible things by having faith.
And why the tree? It was just a tree. Who knows, it probably just grew randomly. No one likely owned it. Even then, he was Jesus. I suppose he could do anything he wanted :
he took an ass and a colt, which we are not told was returned to the owners; he cast out demons and sent them into a herd of pigs and they drowned with no record of a compensation made to the owners even as it is a forbidden animal, so who is to speak for this tree in a public place?
Faith, never the less, has indeed proven to work wonders. It is not a respecter of persons. Whether it is Jesus, or you and I, faith will empower us to do things beyond ourselves if we would step on it.