I'm just finishing up a contract working at a government site for the DOD. I'd say that the average age of the government employees working there was about 50.
The government is not too concerned about hiring old people since they can count on the taxpayers to foot the bill for their health insurance. Small businesses don't have that luxury. They will go out of their way to hire young people.
If you hire a 25 year old single person for a $40,000 a year job, the health insurance premiums for that job would be about $2400 per year. For a 59 year old married man, that same insurance premium would be closer to $10,000 a year.
Now if you have two remotely similarly qualified people applying for that job in your company, who are you going to hire?