What are the benefits of measuring vibration velocity instead of vibration displacement?

Machinery vibration is measured in terms of displacement(microns), velocity(mm/s) and acceleration(). But velocity is the preferred parameter for measuring machinery vibration because most of the equipment failure during vibration is due to fatigue. (Fatigue failure occurs when an object is subjected to repetitive or cyclic loads). For example, consider a metal wire, when you try to break it by applying tension, it requires a good amount of load to fail it. But the same wire when subjected to and fro deflection or displacement, requires relatively less load to fail the wire. This is due to fatigue. Fatigue life depends on how much an object is deflected and its frequency of deflection. Metal wire fails early if the magnitude of deflection and its frequency is high. The vibration parameter that considers both displacement and frequency is velocity since velocity is the product of frequency and displacement.