Most employees view base salary as a barometer of their worth, so thinking about a steady decrease in the amount of money being provided to them has had a psychological impact. That's why organizations looked to variable pay as a way to counteract that -- until recently.
Variable pay is designed to help employees concentrate on company goals and objectives, while eliminating 'entitlement' issues that often arise with a holiday bonus.
Employers recognize that the value in tying awards to performance, as opposed to the holidays, better connects employees to the company's goals and objectives, eliminates 'entitlement' issues, and leads to increased productivity and improved business results.
They're clearly sending a message to employees that they will be rewarded for high performance.