The safety requirements now being imposed on fuel tanks with respect to vapours and sources of ignition, if applied consistently to other systems, would probably ground every commercial aircraft, economically if not legally.
To suggest the industry is dragging its feet over cost is nonsense; the issue is acceptable risk - which is about one catastrophic event per 10,000,000 flight hours, historically, and as embedded in current regulatory and safety practices - and the politically motivated over-concentration on specific risks - like inflight TR malfunction or fuel tank ignition, to name two cases - probably overall degrades safety by distracting attention from the easier-to-address or more significant risk contributors.