For a UK resident VS is an airline which one can fly to many destinations. For a US resident VS is primarily an airline that serves one destination.

VS could have chosen to reduce the number of Tier Points required for status, but no doubt they realize many UK customers would "move" to the US. VS could have made it easier to earn Tier Points on their US-based partner airlines CO and US. This is the solution BA has used with AA.

Instead, VS chose to allow Tier Points to be earned through the credit card, capped at 24 points per year. This does make it much easier to maintain existing Gold status, but otherwise it's no big deal because VS status isn't recognized by most of their partner airlines.