This is the question that stands out among the many received when you start letting people in and being open about your past.  The truth is that there are too many reasons to list them all, and you don't even realize they are there until you look back at it.  If I knew then what I know now I probably would have.  If there were the same resources as there are now, I probably would have.  I say probably because an option being available isn't the same as knowing that those options are available.

Do I wish I'd had options, or known about options back then?   Of course.  It's a bit too late for that now though, isn't it?

So here's my answer to that question.  When you're in it, you don't know there's something wrong with it.   At least you don't for a long time.  When you grow up from age 4 on having it happen, you think it's normal.  You don't think "This is wrong and other people don't treat their kids this way?"  That concept is foreign to you.  To you, all families have this dynamic.  All families have the same thing going on behind closed doors.  All of your friends are going through the same thing and they're not talking about it because it's just normal.  

You believe what you're told.  That you're the problem.  That there is something inherently wrong with you.  You deserve everything that is happening to you, even when you don't understand what it is that is wrong with you or what you did to deserve it.  You don't question that.  It must be true or else the person you depend on wouldn't be doing it to you.  And even once you start to realize you're not the problem, you still believe on some level that there is something about you that isn't worth saving.  Nobody will want to help you.  Why would they want to take in the person you have grown up believing you are. 

Escape isn't an option.  Not until you're an adult and they can't do anything about it.  Until then, if you run away, someone will catch you and bring you back.  And then things will get worse, if that's even possible.  So, while you consider running away, more times than you can count, in more ways than you can imagine... the end result is that fear of being caught and brought back squashes that dream.  You quickly realize that your two available options are to survive to 18 so you can leave and nobody can ever force you to come back, and ending things yourself before they can get around to it.  Believe me, you consider that as an option pretty often too.  An instant end to the pain.  A way to avoid further beatings with no understanding of what you can do to prevent them.  Something you CAN control.  Besides...there's something wrong with you that you don't understand.  You're not worth love.  Hell...sometimes you even think about it as a way to unburden the person doing it from having to deal with you and all that is wrong with you.  

In the end though...the reason you don't run away and the reason you don't off yourself are the same thing.  You want to live.  You want to experience a life free of the fear.  You want to experience a life where someone loves you.  And the only way that is happening is if you endure and survive long enough to be allowed to leave.   Although it may seem long...this is the short answer to the question.  At least for me it is.