Why do movies claim type AB blood people have trouble getting transfusions?

This seems to be a theme in movies and television: a character has type AB blood and needs a donor, but AB is a rare blood type and nobody can be found. Someone with type AB needs to be found, or else they die. I thought AB was the universal recipient, could take blood from anyone.
This happens in Bruce Almighty towards the end. It also happens in the Terminator tv show, the uncle is AB, the mom is O-, and somehow the son is type AB.

Am I missing something or did the writers fail sixth grade science?

You're right; AB is the easiest type to transfuse because ANYONE can give them blood--they are, as you say, "universal recipients." (Maybe those writers should take a genetics class--or else maybe they presume that people watching those shows haven't.)

I should say, however, that it is possible for a child to be AB even if the mom is O. It just means that the father would have to be AB. In the case of the uncle (presuming he is biologically related to the mother), it is possible for him to be AB and her to be O. It just means that one the parents is A and the other is B. This gives equal chance for O, A, B, and AB.

You are not missing anything, the writers are. They are confusing the universal donor O negative with the universal recipient AB Positive.

It is possible for a child to be AB even if the mom is O. It just means that the father would have to be AB. It is possible for the uncle to be AB Positive or negative and her to be O negative. It just means that one of the mother's parents is A and the other is B. This gives equal chance for O, A, B, and AB.

Medically, you are correct.

AB is known as a universal recipient because it can accept blood from any other blood type.

O is known as a universal donor because it will be accepted by any other blood type.

I've never seen the movies or TV shows you are referencing, so I can't comment further on the educational background of the script writers.

agrees with what the others said. also, i think what those writers mean is actually AB NEGATIVE. AB negative is rarer than AB positive. the positive and negative means that the person doesn't have the Rh antigen.