An event that is very possible to happen, hasn't happened. Why? I showed a friend an example of conditional probability, using the formula P(A|B) = P(A intersection B)/P(B). She asked an interesting question (a random question that didn't really have to do with My problem) and I would like to know how You would answer it:
"How do You explain, given a series of events, and knowing that another event is very probable to happen because of the first ones, Hasn't happened?"
She means: An event that is very possible to happen, hasn't happened. Why?
I imagine that this question has various answers. The one that ocurred to me is: Maybe, that probability did not only depend on those events. Maybe there Was a larger Chain of events including independent events, and that's why it hasn't ocurred. 
I'm sorry if my question sounds too ambiguous. You can delete it if that's precise. Nometheless I appreciate Lord_Farin 's answer. It has actually helped me, and is a mathematical answer.
 A: The easiest explanation is:

"very probable" is not the same as "certain"

and indeed, in probability theory, we don't even have:
$$\Pr(X) = 1 \iff \text{$X$ is certain to happen}$$
because the left-hand side does not account for so-called "probability zero" events. Examples of those are:


*

*Tossing a fair coin an unlimited number of times and never getting tails;

*A uniformly randomly chosen $x \in [0,1]$ is rational.


For more information I refer you to Wikipedia's "almost surely" lemma.
A: In reality, what your asking is why aren't all probabilities $0$ or $1$? That is, if something is very likely to happen (given the events leading up to it) always does happen, then the probability of any "likely" event occurring would be $1$ while the probability of an "unlikely" event would be $0$. If this were the case, no one would study probability. In fact, depending on how likely life were to exist, there might not be any life. At that, there might not be any universe, at least not in the way it is now known, if unlikely events never occurred. 
The most mild effect of a probability $0$ or $1$ world would be how boring everything would be. Every movie you've seen where someone had to overcome an enormous obstacle would have ended without the unlikely success of the protagonist. The Death Star would have been a resounding success and Sauron would be at a party showing off his fancy ring.
