Being a celebrity agent can be more lucrative than being a celebrity, but it does require a certain tenacity and a very specific personality type. People who go into the business of being celebrity agents are very social people. They are the people who can go into a room, meet everyone and set up future meetings before you've even tried the guacamole. It's not the celebrity's job to hustle for work and be personable. It's the celebrity's job to perform. That's why it's so crucial to have an agent.
Agents make anywhere between ten and twenty percent of their talent's earnings. That's because they are the ones that find the work for their people. If you're a celebrity who doesn't want to give away part of their paycheck, then you better find the work on your own.