It's all true what you are saying. I'm doing CPR at least twice a week (that's a good week). There is no substitute for training and experience. Little gizmos won't tell you all the subpoints of ABCs. The point that originally was made was that person wanted to have an instruction for others just in case they passed out and were in the need of CPR.

Once in the thousand cases maybe a person will save somebody while performing a cpr out of a cheat sheet. But I bet you they would cause much more harm for the rest of the people they would help. And I'm not talking about breaking sterum or cracking ribs. Did you ever try to do and maintain by yourself a jaw thrust whyle continuing ventilations? It's hard as hell and imagine somebody without a training trying that from the pic alone for the first time under pressure.