I don't think you are being drawn into an elitist area, there are a number of reasons that the SAS type smock is popular.
There is normally plenty of room (people tend to buy them that way), they are quite baggy and allow for movement. This also allows a multitude of warm kit design and materials to be used underneath.
They are quite light in weight and pack reasonably small, both the lighter weight ventile and gaberdine dry quite quickly since they are only doubled in certain areas. Cotton breathes very well, both are strong materials and wear quite hard (ventile is the stronger and more resilient).
The pockets are quite a good size and enable you to get a fair amount into them (they are of a bellows design), the buttons are a good size, when you are wearing gloves the pockets can be opened and closed (not always with ease, but it can be done). If you lose a button in the field and you have a small repair kit, even if you cant find the button, you can stitch in a small piece of wood as a toggle as the button hole will except it.
On the arctic smock you have a large wired hood which is adjustable to suit the wearer and due to its size you can fit most hats, other than ones with a wide brim, on underneath.
When the hood is not in use it can be rolled down out of the way like a padded collar and the cords for adjustment can be used to tie it down out of the way.
But generally people buy them not because of any of this, it's because they are comfortable and in the end that is what we all want. :-D
