The obvious answer is because she doesn't want to.

You keep telling yourself, 'but she cares about me, so why doesn't she call’ and then 2 months after not hearing from you, you realize... That is why she's not calling... because she does care about me.

You see, in your mind you think that if she calls, you can tell her how you feel about her.  Maybe tell her how you've been blubbering for 2 months and that your friends are sick of hearing you talk about her.   Hopefully, you think, if you can just tell her that, she'll see the light and want to get back with you.

But in reality, if she did call, the conversation wouldn't go like that at all.  And once you'd hang up, you're back where the pain all started.

A big part of the pain is, you simply don't want to let go.  All the thoughts and memories, as miserable as it makes you feel, you almost enjoy it because it keeps 'them' in your life.  Without all the tears, the memories will soon fade and so too, them.  And that is what kills you - letting go of them.

At least when you're blubbering, in your mind, you're still having conversations with them.  Going through what you would say if you talked to them or saw them.  Playing over all the regrets, all the 'what if’s’ But what would you really say if she called you... could you have a normal conversation could you talk about your day without your voice getting all quivery like a gay?!  No, you couldn't.  So if you really care enough to send the very best, do just that - send her your best, nothing.  It’s over and she’s telling you loud and clear.
Some advice to get your mind off of it would be, go out and date other girls, go travel a bit.. but all that does is remind you of how much fun you could be having with 'the one'.  So all you can do is just keep living.  Time will pass.  It did before, but it doesn't seem to help.