Quite simply, direct sales is when

Quite simply, direct sales is when a company sells its only products and services ‘directly’ to its client or customer base without an outside party involved.
People say that the shortest distance between two points is a straight line, the direct route, and so direct sales is the conventional approach of selling directly to your customer and cutting out the middleman.
Cutting out the middleman sounds like a good idea at first. Selling directly means that you keep all of the profit; no one is taking a chunk out of your sales. But on further consideration this is not always the case.
When competently analysed, direct sales are full of hidden (and not so hidden) costs - salaries and overheads.
Imagine what it would cost Coca Cola to vend directly to their customers! The costs would eventually prohibit the activity entirely.
Instead, Coca Cola chooses to sell its products through third parties, such as shops, supermarkets and via vending machines.