Contractual doesn't mean guaranteed. You could have a bonus that's contractually tied to a certain set of conditions being met (e.g. personal objectives). If the employee meets those objectives and the company doesn't pay out, they could be in breach, regardless of their financial situation.

They are bonuses, but the word "bonus" means slightly different things in different industries. In the banking industry, think of it more like a sales commission than a totally optional check for doing a really good job. It's paid out according to a pre-determined formula, not the whim of a manager.

Which makes sense. In the cases of financial institutions needing a bailout while simultaneously paying huge bonuses something must be seriously miscalibrated in their calculations.