Yes, it is design that way. Not all fields in a table are needed on a layout. It would be more inconvenient to have to delete the unwanted fields and most users want an customized layout, so it is much faster to just create the layout. There is a setting under preferences, then the layout tab, to add newly defined fields to the layout or you can just add the desired fields to your layout.
But just because you don't see a field on the layout when you leave table view does not mean that you can't go into layout mode and add the field to the layout so that you can specify formatting for it that will then be in affect when you return to table view. When you click "modify", you'll find that fields physically present on the layout have a "lock" symbol to the left showing that they are physically present on the layout.