There are a lot of reasons due to which the plastic furniture is picked rather than wooden furniture. I have stated a few, they are as follows:

* Plastic furniture is inexpensive when compared to wood or metal.  Comfortable and stylish furniture can be made with plastic with a very low cost. 
* It is light weighted.  You can move around the furniture without any help to any convenient locations without much hassle.
* Plastic furniture has low or no maintenance cost.  It is generally unbreakable and does not require regular maintenance like wooden furniture.  On the other hand, traditional furniture made of wood may develop cracks due to extreme climatic conditions and may also require some maintenance like polishing, etc.
* Plastic can be easily moulded to any desired shape and carvings can be easily made to get variety of designs.  Number of new and stylish designs is available in plastic today.
* Usage of plastic reduces cutting of trees and thereby deforestation. This goes a long way in protecting our forests. Wooden furniture on the other hand involves wood to be cut for making furniture which leads to ecological problems.
I hope these points clear your doubt.