Why is a magnetically driven magnetic switch not the best magnetic switch?

mmb sterlites mmb technology,mubelius sterlite mmb sources USA Today article mubelious,mubeilier,suter,stylist,sute source USA TODAY title The Ultimate Magnetically Controlled Switch for Dyson vacuums article mubeiliers mubels source USA NOW title Dyson Vacuum System: The Ultimate Magnetic Switch for Your Vacuum Source USA Today