> doing it cold extracts all the flavours without damage

Well, no, flavors fluctuate with temperature. Temperature changes flavor degradation and dissipation, and what compounds are released or not released. Heat can actually contribute the preferred flavors that may be lacking in unheated brews, and vice versa. Hot coffee can be the best tasting coffee, for a very short period of time. Cold-brew coffee is stable for longer, and has less astringent, bitter, and sour flavors, which lends it a cleaner, brighter flavor, but can make it lack "body". Point being, you still have to taste it hot to find out if it's going to taste good hot.