I'm relatively new to this practice, so please forgive a naive question, but I was wondering why zazen is our preferred practice. I've been reading Charlotte Joko Beck's book Nothing Special and at one point she considers the "subject-object problem", i.e., how we consider ourselves separate from all else. She describes a fruitful practice as becoming "pure experience" such that the subject and object dissolve. She uses the example of hammering a nail - one can become so absorbed in the experience of hammering a nail that the self disappears and there is just the pure experience of hammering a nail left. If I understand her correctly, I've occasionally had "pure experience" writing legal briefs, mountain biking, practicing karate, and hiking. If "pure experience" can be had hammering a nail or whatever, why do we sit? Put another way, is there something that makes just sitting preferable to just doing something else?
I appreciate any insight on this question.