The advantage here is that employees are 1) rewarded for the work they do, and 2) shows that the company understands the value that they bring, 3) the employees become invested in the success of the business because they benefit directly from it (as opposed to a flat "10% bonus based on salary").
As an employee myself, it's hard to look at companies that make massive profits but don't reward those responsible for helping make that happen (the labor force). One could argue "anyone could do that job", or "if it wasn't him it would be someone else", but that doesn't matter. Just because you CAN take all the profits for yourself doesn't mean that you should.
From an economic perspective, funds going to employees are turned around in the economy and generate more economic activity that money sitting in your bank account.