While active cancellation certainly helps you feel more relaxed during your hours aloft, you're still constrained by the physics of pressure, weight, and temperature. But the human factors relating to user convenience are certainly more complicated for ANR headsets. ANR places additional constraints on the cavity and ear seal design. Furthermore, the electronics for cancellation require power, and most are supported by some form of portable power pack. The size and weight of such packs can be a pilot convenience factor, as can various other features available in the newer offerings.
Comfort is a relatively recent addition to the pilot's want-list.
Early on, hearing protection and hands-free communication were the principle reasons for using a headset. The original and most popular headset design was developed for optimal passive attenuation. The focus was on military needs, and thus for noise environments often much harsher than those we encounter in General Aviation. As needs and materials evolved, some changes were introduced to reduce weight and improve comfort. It turns out there's substantial variation in the size and shapes of human heads.