For ages, floor coverings were attached to their underlying substrates. Hardwood floors do need to be nailed down to the subfloor. Ceramic and porcelain tile also need to be mortared to their bases.
As do-it-yourself floor installation gained in popularity, methods had to be developed to ease the complexity of installation for homeowners. Development of the floating floor freed novice floor installers from dealing with manual nailing or air compressed floor nailers. It benefited professional floor installers, too, allowing them to lay down floors at a faster rate.
While it seems improbable to install a hard floor that just sits there like a rug, unattached to anything else, it is a method that makes absolute sense because of three factors:
Sheer Weight: Even though individual laminate planks are lightweight, collectively they can weigh several hundred pounds across an entire room. This unified, large structure is difficult to move.
Friction: Below laminate is foam or cork underlayment. Friction between flooring planks and underlayment controls, but does not completely eliminate, lateral movement. This lateral movement is desired so that the flooring can expand and contract with changes in humidity.
Joinery: Laminate boards positively snap or glue together. This positive joinery means that boards cannot come detached very easily.