Crikey, Miesque! I'm going to Cut & Paste that to my CV!
Well, that's always an interesting one, Slim. Why, indeed? There is often still this business of dependency at work, I think. Ask any women's shelter why a seriously beaten woman will return to a brutal partner, and there'll be a dozen different answers. Why does a parent let a drug-addled son or daughter back home, knowing they'll steal them blind again? Why does an adult keep returning to a parent in desperate and futile hope that they won't continue to feel unloved or unwanted?
There are probably some set, repetitive scenarios well known to counsellors, psychologists and psychiatrists because they occur so often, with a few personal tweaks.
For a lot of people, a return to base camp is because of the time and emotion they feel they've invested in the other person, and that while there was a blip on the screen, however bad it seemed at the time, they'd rather not start over with a fresh investment of time/emotion/money, whatever. Thus, it's less painful - with all the possibilities of another break down, rejection, and so on - to go back to what's familiar, than to venture out to the new.
That's why I think a lot of folks will go back or be taken back - the blemishes may have been dealt with in their own way ("he only hit me once, he'll never do it again", "she only wants money for really nice things, it's not like she spends it on tat", "he's been clean for three months, so let's have him home again") and although it's a bit like a car with a few dings in the side, it still drives like it did, it still makes the same reassuring engine sounds, so why change it for the unknown one which might turn out to be no better in the end? So, there's the dependability of what's known, rather than the risk of what's not.
There's also the feeling that if you go back/get taken back, you're in a stronger position than people who walk away and don't return. They're now vulnerable to the whims and fancy of starting over with strangers, most of the time. You're not. You have a much better understanding of what to expect - whether it's the occasional slap, philander with someone else, poor hygiene, a tendency to lie, a little too much liking for following up on losses or never staying in a job.
You can say it's love overcoming all things, and in some cases that's quite possibly so, but usually and banally, it's about going for what you know best, rather than venturing for parts unknown. ("There be monsters", as old maps used to say. So rather keep the 'monsters' you've already discovered, than go and find possibly worse ones.)
Well, that's my personal take on a lot of it!