Never took one. But a good instructor should prepare a newby on the different techniques of entry, the danger of rough sea, the danger of getting hit by a ladder, etiquette in entry and reentry, poor visibility and danger of surface traffic, the need for staying with the "group" as a boat captain can miss the bobbing black head, while keeping an eye on the large bubble mass, the need for back up lighting for night dives (keep the darn boat from hitting you in emergency situation)....
I can go on and on..... And a person can say the same for shore dives.... The bottom line is - as we trim OW requirement to a bare minimum... any amount of face to face, hands on instruction is better than none.
p.s. my wife is due for both hip replacement this summer, glad I didn't listen to any dive instructor's recommendation for her to dive.