Why don’t more Premier League teams adopt this system?

With the evolving role of the modern full-back, options regarding formational changes have increased for managers, who can now use the greater versatility of their players to switch systems. The 4-4-2 set-up is slowly being phased out in favour of 4-5-1 or 4-3-3, as teams look for greater solidarity and a counter-attacking threat. These two options have been relatively successful when used in the Premier League, but is there another choice for coaches?
Italian outfit Napoli have been a breath of fresh air this season, employing a three-man defence with two dynamic wing-backs. This system allow...