Why don't people incentivize long term sales? For example, instead of giving a commission based on how much they sold in a given year, have each salesperson giv

Why don't people incentivize long term sales? For example, instead of giving a commission based on how much they sold in a given year, have each salesperson given some money based on how many years a client has remained with the company, and maybe extra if the client buys more products later on. That way you're incentivizing sales people to build long-lasting relationships, which I assume is what you want.