If you've succeeded at a firm in the same field, the thinking goes, you'll likely repeat your achievements at the new employer. Also, if you have industry experience, you can add value sooner because you don't have to spend time learning the new business. When seeking a new role, realize the difference between expertise and experience. You can get it whenever you want it. Just sign up for the class.
Young people can have as much expertise as older people.
Often, when potential employers say they're looking for experience, they're actually seeking expertise. That is, they prefer to hire someone with knowledge of the position's key subject matter. But in hundreds of other areas, the necessary knowledge can be picked up on the fly. In these cases, you don't have to be a great expert to land the job. Unlike expertise, experience isn't anchored to a specific context.