Age Discrimination Laws Have Unintended Consequences
Too often, laws have unintended consequences. McCain-Feingold comes immediately to mind. A lot of good that law did about getting money out of politics. Other laws are just confusing. Good luck staying in compliance with the ever-morphing IRS code. A layman can't do it. The laws against hiring discrimination fit both these criteria for bad laws. They have had unintended consequences and employers can easily be out of compliance.
Any sort of discrimination laws have unintended consequences. A supremely qualified candidate can be doubted based on race and gender quotas. But the trend in anti-discrimination lawsuits isn't race and gender. Right now, you're in the money if you're old and want to keep your job no matter how unqualified, lazy, unethical, stupid, or antisocial you may be.
Many companies make stupid -- and smart -- decisions hiring and firing. Lots of times, even when it's legal, it's not right. And lots of times, it's more than right. In fact, there are many firings that don't happen because of discrimination laws -- especially now with the baby boomers creaking into retirement age. These people don't like being old (who does?) and don't want to look at the younger, fresher, harder-working co-workers poaching their jobs. And they certainly don't want to be fired -- even if they deserve it.