Of course we could have found something that met our needs, but we wanted a bigger lot and a newer home and that combination is hard to find in our neck of the woods.
My take on the process: we paid more by building than we would have for an equivalent home and it required much more time than buying an existing home would have, but we get to have things our way (and we put the garage doors on the side!) and we got to dictate the quality of the home. I wouldn't do a custom build unless I was planning to live in the home for a long time (which we are).