That works well for government/military where these sort of things are well considered and organisations have the funding to carry out noise surveys (RAFCAM/QQ).
In relation to the helmet mentioned by the OP, from experience of being on both sides of that particular fence, standard practice for civilian operators is often to use the cheapest available system (often a DC clone), and self install in a lot of cases. Individual pilots who often have to self fund their own kit can't see the logic in spending almost twice as much as a base helmet to gain this capability. CEP on the other hand (or custom moulded VAMPS) provides a good trade off between protection and cost - and unfortunately cost is often what the choice comes down to.