You are correct..it hurts when trust is broken and it's so very hard to earn that back...if ever.
Not sure where you're coming from in what you say. Of course you should know a person before you get involved with them. That's where you determin "common ground" meaning the same values. I'm not talking about that butterfly feeling you get when you first meet someone. That is over and gone within the first year.
I don't think that people have to marry to have a relationship. But most want to. Their reasons might be that they want to be a wife/husband...or they want a family, or they just like the idea of it. Those are not good enough reasons by themselves, but are also not bad reasons either.
You sound young, I'm not sure.
Love doesn't go blind. love starts out blind. Then as you know a person over time, the blindness lifts. Then you see what you've got yourself into there you have your disenchantment. You are right, lots of girls are disenchanted and cry over "lost love" but was probably not REAL love to begin with, just the idea of love. But men do this too.
I'm not the expert here. I've made lots of mistakes in my choices. I only commented due to your comment about how opposites attract and I think they do too...they just don't really stick.