Status, at least when you transition.

In investment banking, people would quickly discover what the top bonus was for their year and report it when they moved on to jobs in, for example, private equity. The banks saw it as symbiotic and would confirm inflated compensation. It made the ex-analysts get better jobs but it also made the firms look more generous, so it was seen as win-win.

It becomes an issue when next year's class expects the middle bonus to be last year's top bonus.