I think that the issue here is that to display EAS requires an ADC. There are two inherent problems here:
1. It is an additional expense for light aircraft, gliders, microlights etc that is, frankly, unnecessary.
2. If the ADC fails, there will need to be a reversionary IAS mode that will display an airspeed that is CAS (unless there are significant static source pressure errors). If operating at high altitude this will mean that airframe limits will have to be promulgated as both CAS and EAS and all 'V' speeds will also have to be promulgated with respect to both airspeeds and, for high altitude airfields, will be different. The potential safety implications for using the wrong set of speeds far outweighs the advantages of having EAS rather than CAS. Until the reliability of an EAS system equals that of a CAS system then I think that we must stick with CAS.
I have been flying for many years over a fairly large flight envelope and cannot think of one instance where having EAS rather than CAS displayed would have helped me.