Ask HN: How to set up two salespeople in the same area?

Let's suppose there's a company is closing medium size enterprise deals. This company knows exactly what it's doing, how to sell, who they need to target, how to target them etc. This company has more leads than the capacity to handle them by the in-field salespeople.

I saw that there's a big aversion from the sales side on to setting up more than one person with the same area. They are afraid that the other one will take good leads. They are scared that they will close all the leads, and lose their jobs.

From the company point of view, it's making no sense. It's obvious that it's better to close all the deals fast. Or is there something that I don't see?

How good/big/fast companies are handling this issue?