I personally believe yoga is meant for anyone that wishes to improve physical and psychological health...
Regular Yoga practice will bring many health benefits on both a physical and emotional level. Yoga teaches you to inquire into the way you use your body, and to use the awareness you develop to refine the relationships you discover ... to become your own authority and reveal the source of and solutions to all the habitual holding patterns and impositions on the body that have been accumulated in life. Achievement of asana by itself is not the point - it is achievment of support without conflict that re-educates the human being into a new paradigm.
It also has the same effect on our thought processes. Spending time with yourself occupying your body and the present moment gives the mind the space it needs to quieten, and this meditative break from the noise of day to day living brings clarity to our lives. Through facing our difficulties with equanimity, we get to become familiar with our habits and tendencies in the mind as well as the body, so we begin to recognise behaviours and responses that may not be serving our higher interests. In the recognition, we get a chance to change.
From what I understand, one of the original purposes of yoga practice was to work out ways of developing a healthier body/mind relationship so that practitioners could move into deeper states of clarity in meditation. So yoga was written about and explained in terms that were appropriate to Indian culture and Vedic thinking and aspirations of the time. Of course Indian culture from several thousand years ago is not going to have a lot of relevance to your average urban dwelling westerner, but the need for effective ways of developing healthy body/mind relationships is probably more important than ever. And practiced with integrity, yoga can be one of the most powerful tools for self development around. I also believe the deeper ramifications of this work should be made accessible to absolutely anyone that is interested in change.
Practicing Yoga is an enquiry into the very nature of our being. And the discoveries we make can serve us in our relationships with the world around us as well as improving the quality of our own lives.