This is simply not true weather you are right or left handed depends on which of your visual feilds is more developed, if you have a stronger left visual feild, you will be right handed, the same follows for which of your feet you find more natural. There is definitely a link however as you said we are creatures of habit and if you originally learn to use left foot forward you will feel more comfortable like that, similar to if you told a right handed child to always hold a pen in the left hand before teaching them to write.
Confusing I know, but there have been some great psychological studies into this.
I personally am stronger with all of my right side, compared to my left.