Because you didn't know enough to appreciate it. But that's why you're in grad school. You got hooked once you realized that the more you learned about a topic, the more interesting it was. Treat your career exploration as another research project. Don t assume surface appearances are correct.
Academic life is one of about ten million possible careers.
It's too late to change careers. In a world where layoffs and takeovers are commonplace, the job market is full of people scrambling to update their resumes, leap into different fields, or start over in mid-career. There's no shame in changing tacks. The key to successful career changing is learning the customs and vocabulary of the field you want to enter and then articulating your value. The tenure-track model of having the same job for life is outdated.