Actually they don't consume a very large portion of the overall spectrum at all. Nearly all the bands you mention are in the Mhz range or less rather than Ghz

Actually they don't consume a very large portion of the overall spectrum at all. Nearly all the bands you mention are in the Mhz range or less rather than Ghz and as a result they're not really even suited for WiFi use. The lower frequencies are less optimal for high speed data transfer and also broadcast to a longer range, as well as penetrate buildings more easily than their higher frequency counterparts. As well as that those bands are already heavily used already - it would make no sense to open these bands up to WiFi.