Some good points made here. Stretching should never be done before a workout as it stimulates the para-sympathetic nervous system to fire, causing the body to relax, thus the muscles become weaker and there is a greater chance of injury. Stretching after a workout has been shown to help blood flow and recovery time though.
With regards to the question if stretching is necessary, well it depends on ones overall posture and what activities one performs. By sitting most of our days many people have tight muscles and should stretch them. On the other hand, being to flexible has it's downsides too as we need that tension to hold our joint in place. Gymnastics who have the muscle to keep their joints in place may not have any issues but others, say yoga fanatics, who do no strength training have and are excessively flexible do have problems.
Thus to answer your question simply, if we lived in a pale world, stretching wouldn't be necessary, but since we don't, it is recommended for most to some degree.