Cork is hard to get because it is a natural material that is only found in certain parts of the world. It is also difficult to harvest and process.

Quercus suber, commonly called the cork oak, is a medium-sized, evergreen oak tree in the section Quercus sect. Cerris. It is the primary source of cork for wine bottle stoppers and other uses, such as cork flooring and as the cores of cricket balls.

Benefits of cork And it is used for many things, from the production of agglomerate for walls and floors to the manufacture of shoe insoles and even the lining of satellite capsules, but its main purpose is the sealing of bottles of alcoholic beverages -wines, spirits and cava- in the form of stoppers.

I think the whole boiling and soaking thing is a holdover from the old days of winemaking. Back then corks were not very pliant and had to be softened by heat. In addition, water acted as a lubricant to help the corks get into the bottle. Also, corks were not very clean to begin with.