When Opportunity Attacks

Self explanatory

So after literal years of abstinence, I began roleplaying again with some friends. I was never super experienced to begin with so I still play like a noob, and I'm ok with that. Some things I remember well, others it's like I'm playing for the first time ever. In all actuality, this is the first time I've played a Pathfinder campaign, so I guess that's true in many regards.

At any rate it was a fun - and educational - experience.

One thing that I can never quite comprehend (and this was true from my old D&D days as well) was the entire concept of "attack of opportunity." I mean, humor me here. Assume we live in a world where humans, elves, halflings, orcs, dwarves and the like live together and for no real reason often choose to set out for adventure and conquest. All that aside, let's try to rationalize the attack of opportunity.

For those of you unfamiliar, it goes something like this.A bad guy (in last night's instance it was a giant firebeetle) engages me in battle. He attacks with his pincers, a little stabby stabby, and his turn is over so we are left standing directly side by side. My turn comes around and like any wise halfling (especially one who uses a bow), I think it might be a good idea to move from the monster. I mean, halflings aren't necessarily the bravest of things, and this beetle is four times my size.

This is what happens when
you try to run!

Well here's the deal. If I am standing next to a monster and then run away, that monster gets an attack of opportunity against me, where he can freely attack the crap out of me and often kill me. No bueno. However, if I only move one itty bitty step away, he does not get the attack and I am free to stand and finish my turn without him getting a free attack.

Great. So let's go back to visualizing this as a real battle. Let's assume, yes, ok, you get an attack on me for catching your attention as I run off. Fine. Beat me up as I run with my little bitty legs as far as I can muster. But if I'm only side-stepping you, what about that motion makes you not want to attack me anymore. Aren't I easier prey than ever when I'm standing right there?!? Wouldn't you see me scoot right over there and reach out your arm and go bam! right in the kisser?

But for some reason, you don't.

This makes no sense to me. None at all. Either attack me because I try to run away, or leave me alone. But this silly little glitch of a rule - while I admit is super advantageous for me - is the dumbest thing I've run across thus far.

So if opportunity strikes, just attack me. Make it easier for us all to understand.

Braaaaaiiiiinnnn Food: What rules for tabletops drive you absolutely batty?