Some people are just WAY ahead of their time. Like the good Inspector here, he gave you a clue a long time ago. That the Trench coat can be worn as a fashion statement, and not for just snooping around. Like so many other classic pieces in a wardrobe, the trench was not invented for the purpose of fashion, but to serve as an alternative to the heavier coats WWI British soldiers wore while in the trenches, hence the name. Made famous by the Burberry label (who also designed the original) and later the London Fog brand, trench coat have become a classic silhouette in the fashion industry. Worn by men and woman, in different lengths, and in various colors, it's safe to safe that it's not going anywhere no time soon.
So to all you fashion "Columbos" and "Dick Tracys" out there taking claim to bring the trench coat back, get a clue. It never left.