Why have Town Hall outside of farming base?

From what I understand, the point of a farming base is to minimize the loss of resources when you're attacked. When a Town Hall is destroyed, you lose gold equal to the amount stored in your fullest Gold Storage building. So putting your Town Hall outside your base in the hopes of low-cost shields means you will lose a LOT of resources when they come and destroy your Town Hall.

Why then do the farming builds suggesting the Town Hall being outside of the base?

The town hall used to hold only 1000 gold and 1000 elixir. Plus, destroying the town hall would provide an immediate shield. However the December 2015 update completely changed the shield mechanics and the town hall capacities. Any farming layout suggested before this update is no longer valid. Here is a post that details how to build a farming base now, and avoid common mistakes.