People who are otherwise slack in their outlook at life are the type of people who would think of taking marriage not so seriously or in other words be afraid of the commitment. They do not realize that married life is not just the physical attraction. Over a period of time, marriage develops into its fullest with the deeper intimacy and emotional involvement of two people. 

Most popular belief to have a trial marriage is that it helps in knowing the couples better and if they would get along. The fact about married life is that no two people can get along without the constant efforts on part of both the partners. It is an ongoing process that ends, as I foresee, with the life itself. The human mind is so mysterious that some time the couples may agree in fullest on a certain issue and disagree at that very issue in a different state of mind. This could surprise the two very people involved. After living together for a couple of decades we could say we know each other well, probably not. The only thing we know is to forgive and forget and that the intentions of the other person are not bad. No two people living together stop annoying each other or for that matter stop affecting each other's emotions. Emotions do not die.

People who are for cohabiting before marriage do have various reasons and justifications. They have all the advantages of a married life but at the same time not required to pay for the bills of the other person, no commitment, being able to leave if things got rough. They do not have to suffer the pain of a divorce and no responsibility of children. They do not have to take care of the home and the kids and most important they can leave whenever they want to. Someone who would think like this in my opinion is not ready to get married at all. 

On the contrary, anyone who would get comfortable living with someone without the commitments, would make it really difficult for him to adjust once he commits. The sudden show of rights can drive people crazy. Its not just that - once you know the other person cannot cross his/her boundaries and move into your space, it would be really difficult to accommodate. Emotions are not like a toggle that you turn on and off. But once you start as a married couple you are willing to let your partner move into your territories and it is much easier to accept because you are aware of the advantages the married life has to offer. You are clear as to what you are giving to receive in return. 

Nothing is free in this world. Whatever you get you have to pay a price for it.