Why do you think creatine is so infrequently used? For example NCAA athletes routinely do not use it, it's considered almost a fringe practice in Division 1 basketball since the training staff can't recommend it (for whatever reason).

Furthermore I'm surprised at how we have so much of a "gym culture" yet the highest protein shake you can buy at my big box is 25g of protein (Muscle Milk). When 1.6g/kg for me is 120g, I'd need 4 of those if I'm otherwise not eating a high-protein diet. I'd say a lot of people cheat themselves out of results from strength training by underconsuming protein, especially dieting women.