Why aren't all bishops infallible?

[SirEwenii]

If the bishops are the successors of the apostles and they have apostolic authority why aren’t they also infallible in matters of faith and morals? Clearly they aren’t add there have been many heretics, but how can they have apostolic authority if they’re not infallible?

 

[Fr.Charles_Grondin]

Jesus to Peter:

Jesus said to him in reply, “Blessed are you, Simon son of Jonah. For flesh and blood has not revealed this to you, but my heavenly Father. And so I say to you, you are Peter, and upon this rock I will build my church, and the gates of the netherworld shall not prevail against it. l I will give you the keys to the kingdom of heaven. Whatever you bind on earth shall be bound in heaven; and whatever you loose on earth shall be loosed in heaven.”

Jesus to all the Apostles:

Amen, I say to you, whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven.

Notice that Jesus singles out Peter in a particular way. It is Peter who is the rock on which the Church is built and Peter is the only one to receive the power of binding and loosing in a singular manner. The other Apostles also receive this authority but it is given to them as a group, not as individuals.

Thus the Church teaches that the Successor of St. Peter (the Pope) teaches infallibly of his own authority and all the successors of the Apostles (the Bishops) teach infallibly when they teach as a group (i.e. Ecumenical Council).