They don&#x27;t necessarily have to, that&#x27;s true. But if there was any appetite to have gargantuan 500MB+ decompression libraries to save 20 or 30% on downloaded bytes while browsing, we would have seen much more uptake of existing simpler compression schemes like SDCH which takes a tiny step in that direction with a relatively large (but still tiny) pre-built dictionary for the WWW.