Having boundaries is the first thing I worked on when I started therapy, and it was something I wish I would've grown up with. First, you respect yourself more when you realize that you can say no when you want. It's so much easier to realize when someone is taking advantage of you. You start to realize who you are, and what sort of people you can get along with, and you know when someone is abusing or disrespecting you. It's a LOT easier to communicate, and be able to tell someone how you really feel about something, and why. And one of the biggest things is you know when a problem is yours, and you don't let people mix you up in their feelings or problems.
Knowing where your own boundaries are is essential to a well-lived life. If you don't have them, you are essentially powerless to consciously fulfill your own desires and expectations. You will be prone to expecting others to fulfill the for you, and that won't happen. You set yourself up for failure when you don't know who you are.
because you will end up becoming some else's servant
Because if you should ever run into a person that wants to challenge them, for example a Narcissist, you'll be able to maintain them....it's really an important thing to do. I didn't know how and I got hurt.