Age bias tells young people that they have no future in the IT industry
Everybody becomes an older worker eventually. Who wants to have a career that lasts only 10 or 15 years?
Age-bias is discouraging even the younger people from going into the IT industry. Because it doesn't make sense for young people to invest a lot of time, money, and effort into a career that won't last.
The way employers treat older workers shows younger workers how they will be treated, when they get older. Which means that age bias probably has a demoralizing effect on both older and younger workers.