Interviewing is fundamentally an exercise in risk management. As a job seeker, your goal is to reduce any appearance of risk in hiring you.
If you are looking for a job just like the one you have now, no problem -- you already appear safe. But the minute you try to climb one rung up the career ladder or change careers, industry or functional area, you become more risky in the eyes of a potential hiring manager.
Let's say your industry is in decline and you just saw an ad for a growing industry that you'd love to jump into. You think, "I could easily transfer my skills to that exciting new environment." So you send in your resume. But when the hiring manager skims your resume, she thinks, "Meh, it's probably safer to hire someone who already has experience in my industry."
For you, that's game over. The plain fact is that no matter how cleverly written it is, your resume usually won't help you to make a career change. You need to learn smarter ways to make a personal connection with a hiring manager.
But even the best networking will not help you make a career jump until you understand a few fundamentals.