The original never had this filter but StarCraft 2 does "because we can," says Blizzard. It just wasn't possible then, but resources are strong now.
"While players are encouraged to share the maps they create through Battle.net, published maps are subject to review to ensure that they promote a fun and safe environment for all players," Blizzard community manager Lylirra.
"If a map is found to contain inappropriate content, it will be removed from Battle.net and the map maker will be contacted via email." A player asked why Blizz have decided to 'police' StarCraft II maps when they didn't bother with the original.
"Because we can. Literally. We have a support department now of size and ability to enforce these types of things. It simply wasn't possible when our in-game support used to consist of approximately 20 technical support agents," added Bashiok.
"We did, however, actually police Warcraft III maps to a small degree if they were reported. But it was a rather archaic process." Battle.net no place for map smut peddlers.