In it's modern expression, (postural) yoga can appear to be a personal endevour.  That is, we work on ourselves.  Typically, yoga is a thing that you go to a studio or center to do; it is done under the tutilage of a guide; your relationship and the topic of conversations between yourself and this guide will primarily be about the physical feats of a yoga asana practice and the questions that come up along the way.

One could be forgiven, with all this focus on the body, for thinking that yoga is a personal enrichment program.  A kind of self-help. Generally speaking, we all come to yoga looking to fix something about ourselves.

Somewhere along the way, we will hit barriers.  We might be humbled.  We'll realize that we can't, through will power alone, get what we want.  We'll also start to realize aspects of our own character we'd not understood before: how we react to difficulty, for example, or what we tend to do with fear.

So even a purely physical practice, in which no text or philosophy or psychology is mentioned, we'll find ourselves in much deeper territory than we'd intended.  Yoga asana can be a kind of proving ground: some of us find this depth intriguing and jump in; others of us turn away and find some other way to exercise or deal with our problems.

With it's focus on the body and the physical benefits of yoga asana, the deeper teachings of the yoga tradition are often neglected.  They aren't exactly in demand; in a commercial society the customer is always right.  

But there are deeper teachings. 

In a post (post, post) modern society questions of justice, equality, personal and social liberation are more important than ever.  They are also more confusing and overwhelming than ever before.  So many people turn to a yoga tradition because traditional places of ethics and morality no longer speak to us: we come to a yoga studio because we're running away from a church.  And yet we're concerned about meaning: it can't all be relative, or it's every man for himself.  There is such enormous suffering, and through global connections we are more aware of suffering than ever before.  Without morals, life boils down to cruelty.  

Without hope, humanity rots.

Yoga's clarity of ethics have appealed to me from the very beginning.  Understanding them and studying them in greater depth has been the work of my entire teaching career.  As the world spins deeper into conflict and turmoil and individuals and more and more aware of how they can't get away from social troubles, it seems to me teaching yoga as ethics fills a profound need.