While many airlines have robust training departments, there's still a significant number of companies that focus on crew training independently of an airline. The idea is to have an option to select a training provider under a contract under the same way fuel contracts are laid out.
Potentially the larger the airline, the less the benefit, meaning very small aircraft (which are currently useless) could be made a little more realistic by getting a break in the training costs. Conversely, the larger the airline the larger the benefit because of scale.
Hell, make it super complicated and say that an airline can set up a flight training department for some magically large amount of money, which then other airlines could contract to. Blah. I know this is going to get a -.