Composite wood is a type of man made wood mixed with plastic. Many people choose this type of wood is because it is maintenance free. However the real reason is that for this type of wood, there is no way to maintain it.
If there is any scratches, it will be there forever. Unlike natural wood which you can sand the wood and re-varnish it again.
Plastic decking tends to warp overtime too and it gives the unnatural look.
Natural timber tends to be more lasting in the market and people have been using it for years.