I think there are several reasons gnu. Sometimes it is simply the TV direction, which does not show you a proper perspective to allow you to understand what is going on. Also, however slow it looks at times, the game is actually astonishingly fast and requires huge amounts of natural stamina and athleticism at this level. The players simply can't get there in time to keep up. I think another thing which has been happening increasingly over recent years, is that most teams play with two lines of four (or some variation on this theme). To break through these defensive lines, the attacking teams often have to concentrate several players in small areas to achieve a fast build up. This can lead to them becoming bunched on one side of the field.