The first and probably the biggest point in favour of and shop displays is cost. It is one of the cheapest materials around and also one of the most versatile so there is no wonder it is used in everything from cereal boxes to shoe linings, egg cartons to cavity wall insulation.
It's also one of the most readily recyclable materials commonly found around homes and shops. can't be simply be put out for council collection with the rest of the everyday recycling. Paper and cardboard that are made with recycled content are also common and in most cases they are just as good as their non-recycled equivalents. On the other hand, it'll take a lot longer for PVC banners to reach the end of their useful lifetime. Cardboard is many things but incredibly durable isn't usually one of them.
and advertising materials are not that tough unless they are laminated or sealed, in which case they usually can't be recycled. Plain paper and cardboard are certainly not waterproof under ordinary circumstances and once wet they'll never quite be the same, even if you go to the trouble of careful flat drying and ironing.
There is a place for cardboard and a place for canvas, PVC and other plastics. For short term or exclusively indoor applications cardboard is usually just fine as long as it won't be used too roughly, but for outdoor banners or graphical materials that need to last for years, plastic is almost always a better choice.