Why not many people use VFD Inverter constant pressure booster pump?

Most of the VFD / VSD Inverter Constant Pressure Booster Pump are very expensive
Most of the VFD / VSD Inverter Constant Pressure Booster Pump does not have good quality and cannot last long
Most of the VFD / VSD Inverter Constant Pressure Booster Pump does not save energy
Most of the VFD / VSD Inverter Constant Pressure Booster Pump is not user-friendly and can only be installed and set up by very professional technician
Most of the VFD / VSD Inverter Constant Pressure Booster Pump is not easy to do the maintenance and service for