Yeah, tolerance to cowashing isn't as high across the board as certain curly "hair specialists" would have you think IMO. It's just not appropriate for everyone and many people NEED shampoo either regularly or here and there for the look and health of their hair.
And then there are so many possibilities in between strict cowashing and using shampoo for every wash: like watering down the shampoo before using it, or adding a bit of shampoo to the cowash either sometimes or often. Or "lo-poo", of course. Or just using non-sulfate shampoos (though use of a lot of conditioner and/or stylers can eventually lead to a need for a one-time clarifying sulfate shampoo).