You will see asanas in perspective by knowing them as the means to something, and not as an end in itself. Yogic journey is a long one, across lifetimes. But on the way there are many stations, physical well-being is among the early ones. Asanas provide exercise to the rusting parts of the body caused by mechanical, sedentary and stressful modern life-style. With greater physical proficiency, one loses the extra pounds, enjoys better health and acquires overall vitality.
One can make this well-being as the destination and be happy. But, this is a side-effect of asanas the way they are designed. A true potential of asanas goes beyond physical well-being. In yoga-sutra, it mentions asanas as ‘stable and pleasurable (posture)’.
In the context of a gross-to-subtle hierarchy of physical, astral and causal bodies that we, the humans, are a steady physical posture has to evolve into an emotional equi-poise and a discerning (not discriminating) intelligence. Even while doing simple asanas, one needs to watch one’s breath, mind, will-power and energy sources as the inner drivers of all physical actions. Asanas are then a manifested effect of one’s subtle self. Asanas thus can provide a pathway to one’s subtle self so that one can bring the inflexible physical under conscious control of the subtle. All this happens in asanas, the key is what part one is aware of - the gross or the subtle.
Yoga sutra narrates asanas as the first of the eight avenues of practice. But all are equally important towards the final goal of self-realization.