Why is it so hard to leave a toxic situation?

Last night I asked the question on twitter "Why is it so hard to leave a toxic situation?" No one actually answered but it was RT'd a few times, which makes me think I am not the only one who just doesn't understand the logic.

Now, before I start, let's not get it fuc*ed up twisted for one moment I myself have been guilty of this, so their is no judgement in this post. 

We all know that friend --she is miserable, has said she doesn't want to deal with this anymore, and is simply existing as a zombie at this point.  What I don't get is why they start making "excuses" about why they can't remove themselves?  Seriously they have given whomever will listen every reason in the world why they can't leave and why they need to remove themselves from this toxic situation, all in the same breath.  I am really at a lost --what do you the good and caring friend say to them at this point?  This is also the same friend because they are so miserable can never be happy, celebrate, and/or encourage anyone about anything. At some point you start not wanting to talk to or share with this friend.  The saying "hurt people, hurt people" is nothing but the truth.com!

I in no way would tell someone leave their spouse and I know the group of women  I consider friends would never as well. What  I would however tell a friend is to do what they need to do -- that living a happy, drama free, and productive life can't exist if they plan on staying in a toxic situation.  I actually told my friend (who is going through this right now) to pray, be still, and listen!  But while she is doing all of those things I told her she needs a plan on how she is going to live the rest of her life. Was that good advice? I think so, was there more I could have said, sure! But in the end leaving/removing herself is a decision she has got to come to on her own!

I know leaving is never easy especially if their are children involved. Now some would say that the unhappy person is making a sacrifice for their children by staying and they should just suck it up -- I simply do not agree.  While they are miserable everything and everyone they touch feels that misery. How is that productive when trying to be a parent and raise kids?  How will their misery affect the child(ren), cause it surely will?

So back to my question -- why is it so hard to leave a toxic situation??  Is it comfort? Is it fear of the unknown? Is it hope ("Hope is the enemy")? Is it the sex? Is it love? Is it time spent? When I think back on the time(s) I have actually stayed in a toxic situation the reasons are unclear to me...crazy I know right!

So then the question becomes well what do you consider toxic? -- and to be honest this is really subjective. Toxic is a very strong word, I know but if someone or something is causing you not feel alive, always on edge, always fighting, not able to trust, not wanting to be in the same place as it, crying until all your tears are gone, to be sick, to be always in a state of anger or sadness, and a host of other things...well EYE consider that toxic.  If you can't find anything positive or good in your current situation why are you still in it?

What are some of the reasons YOU have remained in a situation you knew was toxic? Or, what are some of the things you did to remove yourself from that toxic situation?