whats the point of suporting the 3GS the tech is super old
Because this is the "free" iPhone (someone said it was a $1.00) you can get with a 2 year contract at AT&T and Apple is still selling it unlocked (~$300).
Presumably it'll fall off the update cycle (no iOS 7) after the next gen iPhone comes out.
Frankly since Apple is selling 3GS new, they should have as many features enabled as possible (that work acceptably) - typically the folks that would get a 3GS wouldn't be getting a 4S features or not (not sure that carries over to the 4).