Why self bias is not suitable for enhancment type mosfet?

With the E-MOSFET, VGS has to be, 'greater than VGS(th) to get any drain current at all. Therefore, when E-MOSFETs are biased, self-bias, current-source bias, and zero bias cannot be used because these forms of bias depend on the depletion mode of operation. This leaves gate bias, voltage-divider bias, and source bias as the means for biasing E-MOSFETs.