Why do we need a method for meditation?

I remember when I first started to meditate to be a bit reluctant about using a specific meditation method. I could not understand why one needs a meditation method to close the eyes, rest the mind while disengaging from thoughts. Why is not enough that one sits down and let the consciousness flow?

As S. Veda Bharati beautifully wrote: 

Although it is true that … Consciousness flows wherever one invites It, the problem, however, remains that the human personality is very much subject to the vagarities of the subconscious. Once we close our eyes a myriad of egoistic fantasies and dreams invade our minds. Useful methods of meditation teach the aspirant to discriminate between what arises from the subconscious and what comes down from the superconscious. We start to meditate and almost immediately our mind wanders off – What to do? How to avoid it? The teacher and the meditation method give us a solution.