Am I Missing Something Here???

Alright ya'll...
I just don't get it - WHY do some women stay in relationships with trifling men? So, I have this friend, lets call her "Shit For Brains" (SFB for short), she is beautiful, intelligent, friendly, sociable, loyal, makes good money - the works. Anyway about 2 years ago she met this guy, let's call him "Dumb Ass" (DA for short) at a club (shouldn't this have been warning sign #1?). He was tall, dark and handsome (to her at least, but hey, different strokes for different folks), funny and said he just moved here from out of state. They exchanged numbers and three weeks later - he was LIVING WITH HER! WTF?? Now, his story is because he JUST moved, he hadn't found a job yet, and his car was being "shipped." Fast forward 2, 6, 8, 12, 15, 22 MONTHS LATER and he still aint got a job and STILL doesn't have a car! Was the car lost in transit or something? Does he have a stash of cash hidden somewhere? How does a 27 year old man survive that long without a car or a job? The answers are - on LIES, a naive woman and his momma.
His initial story to SFB was that he played for the NBA and was injured and living off NBA retirement money (lie #1, we found out later that he never attended college or stepped food on an NBA court). Does DA have any brains? Doesn't he know there's a very popular and accessible tool call Google?? The dude I was dating at the time actually played basketball for the college DA claimed to have played for - he started asking him all these questions at a BBQ we had and DA was straight up embarrassed because he didn't even know the coach's name! (By the way, you need to play in the league for 5 years before you get retirement - and he claimed to have graduated from a 4 year university - which means when she met him in 2003, he would have had to be AT LEAST 27 years old at the time to make this work - he had only just turned 25).
At that moment, I would have dumped the loser out of sheer embarrassment. But NO, she made some BS excuse and continued on. The next BIG thing was that when she paid her rent (she pays ALL of it, he helps with NO bills) the check bounced. She goes online to check her account and finds that 2 checks for $400 each have been cashed by no other than her boyfriend DA!! OH HELL NO!!!! He made up some dumb ass story about how he DID ask her if he could write a check to himself and she must have forgot - and the reason that he wrote 2 is that he thought the first one didn't go through! So let me ask you now folks - Do you think she left him?? Answer: Hell no!! SFB was mad for a hot minute then kept on!
Next incident: One day, SFB is checking her email and gets a new message from a friend. In it, is a link to a profile on match.com - she opens it up - AND THERE IS HER MAN - cheesin for a profile picture! OH HELL NO!! His profile reads something like this "Single professional basketball player, college educated, momma's boy, lives in Westwood, looking for love.." or some BS like that! In the profile pics, it has a picture of him leaning against SFB's car - with a caption that reads "Me and my Baby." (She has a newer Range Rover). She proceeded to make a profile and have back and forth conversations with him without him suspecting a thing. He said he had been single for a long time because he didn't like the groupies that he attracts being in the NBA... When she finally confronted him he of course, denied everything, then went on to admit that he was just playing around and would never cheat on her. OMG - on the real - I thought that THIS was the icing on the cake that would send her foot up his ass for SURE! There are so many more things that have happened from his "former" girlfriends calling her HOUSE, to finding numbers in his pants pockets, to money missing from her purse, to charges he made without her permission on her credit card (Namely the match.com sign up fees and clothing), I could go on and on...
About 2 months after the match.com incident, she comes up pregnant and she recently had his baby. He FINALLY got a part time minimum wage job (she said if he didn't get a job then he couldn't drive her car anymore) and he STILL isn't helping with the bills. He refuses to help with the baby (including watching him while she works - he sits at home all day and plays X Box while the baby goes to a sitter) and does absolutely nothing for her. She sounds miserable every time we talk, but she won't really talk about the situation anymore (plus, I'm sick of hearing about it!) When I ask her why she lets him continue to sponge off her, her answer is simple - "He loves me and I love him, he is trying harder and I think he is working toward being a better man."
Although this situation is extreme, I know plenty of woman who have tricked off their integrity for a man and have stayed in horrible relationships - WHY DO WOMEN DO THIS?
Questions:
Have you ever been in a relationship like this? Do you know anyone else who has?
If so, how did you/they get out? Or why do you/they stay?
Why do you think women subject themselves to this?

Until next time,
Love, Peace & Hair Grease!

"Love is like war; easy to begin but very hard to stop."
H. L. Mencken