Some employers have negotiated a program that waives young driver surcharges. A few of those codes can be used by employees for leisure travel.
Most agencies either have a young driver surcharge or don't allow young drivers to use some of the discount codes which effectively charges those drivers a premium.
You need to shop. Some agencies have lower surcharges.
Hertz has eliminated young driver surcharges in most locations for most cars. You might get a better rate paying the surcharge with a different agency.