People will always be emotionally attached to a relationship, no matter how casual. If you are not emtionally attached to it, then what's the point of even being in the relationship?
But in one of your "casual" relationships, the woman doesn't even have you. Humans do not need a "shock to the system" to make them see that committment is not needed for a relationship.
I have a reason to believe that you are the one who needs a "shock to the system", so to speak. Relationships are about being committed, not being casual.