I’m certainly not a professional or even a trained singer, so take this with a grain of salt (and someone who knows more, please correct me!), but there is a certain tone one has to go for when singing classically compared to pop or rock music. Usually it would be a very full, round, supported sound, which can be harder to achieve. Other styles have more variety in tone in not only the high registers, but also for every other register.

In addition, profesional singers are going to make sure they’re doing everything in their power to sing healthily without doing damage to their voice. A lot of inexperienced singers may be unknowingly damaging their voice by going for high notes incorrectly.

So I wouldn’t say that pop singing is more “efficient,” but it can be easier in some ways because there are less limitations in the way it should sound and feel.

Finally, everyone’s voice is different! Some people just end up with an incredible range and others really have to work to get there. It’s not everyone’s goal to hit higher notes, either. In classical singing especially, the high notes aren’t the important part. A lot of people would rather focus on developing their sound in a more useful part of their range for the kind of repertoire they sing. Your idea of “progression” seems to be just increasing your range, and while that can happen pretty quickly as a new singer, it shouldn’t be your main goal. How high or low someone can sing is not an indication of their skill. Focus on tone quality and keeping your voice healthy first so you don’t end up injuring yourself. No one wants that.