Everyone is used to some degree, so what's the argument about abuse? Your boss needs your skill, but not other stuff, your spouse needs your money and/or potential. Well, of course, it is possible to be taken advantage of.
I was taken advantage of once when I was in a relationship that turned into a mentally abusive relationship. Turns out he only ever wanted me for the money he could get out of me as he pretty much took control of all the money. I finally opened up after years of being told no one would believe me and I got out I am now in a better situation because I spoke out.
It's awful when you end up in a situation where someone will do nothing but take and never give anything back. All I can say is if you are ever in this situation and you know it's not right, don't ever be scared to speak up.
I've been used many times by my ex wife for money. She'd always blow my paychecks and then towards the end of our marriage, she wanted nothing to do with me. She started seeing other people. We had a very toxic relationship that resulted in her gas lighting me and pushing my buttons when she wasn't getting her way. When things got real bad, she'd involve her family who already hated me. Her mom had asked me to divorce from her a year before and let her take the kids. Her family treated me like I was a very abusive person. Our issues eventually reached a "no point of return". One day she showed up at home and begged me for a divorce and confessed to having several affairs outside of the marriage. So after a few months, I went and paid a lawyer for a divorce.
I'm a firm believer in balance in all things, including give and take situations. I know people who are predominantly givers and the amount of emotional and financial abuse they endure is heart breaking.