My guess is that some of us, as we become more experienced and faster, become more comfortable in the pain cave and our minds let our bodies push harder. I agree that max HR is in the "cool but useless" info category.

My HR during a 20km TT is in the 160-162 ballpark. Doing 20' threshold intervals it gets into the low 150s. At my normal cruising speed, it's in the low 120s. That last part used to be in the 130s and decreased as I've gotten fitter.