They call it the curse of competence-the idea that you're too valuable to promote. It's easier for management to keep you in your current position than to find and train someone to do what you do so well...and in the meantime, your career stalls out.
Are you doing your best work? Have you been told how valuable you are in this role? Has your boss been in her position for 100 years, still content to do the same work? Do you have a job that no one else is willing to do? These might be signs that you're stuck because you're too valuable to promote.
But be careful not to use this as an excuse. Take an honest look at the situation and don't assume that you're not being promoted simply because you're so great at what you do. There are ways to circumvent the curse of competence:
Voice your concerns. Do decision makers know you're interested in moving to a new role? The position doesn't have to be a promotion-sometimes a lateral move can be best for your career if it allows you to do and learn new things. But no one can know you're interested if you don't speak up.
Hone additional skills. If all of your skills are related to your existing field, you're more likely to remain in that field. So branch out! If you're in marketing, but really enjoy recruiting talent for your company when you're out and about, take a course in human relations, psychology and the like. And be sure to make management aware of your expanded skill set.
Choose your friends carefully. If you're interested in another line of work, seek out people who work in that field. Are you an IT nerd who wants to turn your love of gardening into something more? Make friends with building and grounds people. Volunteer your time in the area of your passion and build relationships with those who can help you.
Assess your options. Do you want to stay in your field but find that the higher ups really believe you're too valuable to promote? If there is sincerely no opportunity for promotion (and you've spoken up, applied for other roles and are working to the best of your ability), then perhaps it's time to move on. Just be sure you've given it more than a couple of years. Careers are long games. If you quit before the second inning just because you don't like where you are in the lineup, you'll likely be seen as a job hopper rather than someone chasing a promotion. Employers still want commitment and dedication from their employees.
Being too valuable to promote isn't all bad-it means you're really good at your job and appeasing your supervisors, and that's a good thing! But the curse of competence isn't a death sentence. There are ways to grow your opportunities and enjoy the magic of moving up!