Hey Sultan! Welcome to the forum. If you are looking for some very nice scenery, you have come to the right place.
On the question of styrofoam.. I guess it's easiest to work with (along with foamboard and balsa wood), versatile and durable enough for table top wargaming bit still leightweight so you can carry your stuff to meetings etc. too. Wood might be a little too difficult and time-consuming to work with for most people, and seeing that scenery is just one part of the hobby (and the least important to many), that time is spent on modelling, painting and gaming instead.
However, if you want to see and awesome plywood table, check this out: