I have a 4s model. I have WiFi enabled and do search the internet with cellular without wifi. The only thing I can think is I don’t stream videos with the phone and have no add-on apps to do such.
Huh, I guess you got me... I don't stream video either...
Maybe it's something not available on the 4s (wild-ass guess). I've pinged Swordmaker to this sub-thread in case his greater knowledge of the products can shed some light on the Case Of The Missing WiFi Assist. :-)