When my parents' generation used to talk about wallpaper, they meant that piece of colorful paper that would be glued to the walls, instead of painting them. The wallpaper was preferred to painting because it was sometimes cuter than any pattern that could be created by paint and it was also supposed to endure more than paint. My head is full of images of couples moving into a new house and going to choose the proper wallpaper for the dining room and the children's room. They would come back with huge packages in which the wallpaper was wrapped.
Nowadays when we say wallpaper we actually mean desktop wallpaper, which is the cover of our computer screen, what we see in front of our eyes when we stop working for a few minutes and close the applications. For people who spend a lot of time in front of their computers, the desktop wallpaper is much more important than any element of interior design at home. And, since more and more of us are spending their time in front of the computer, then the desktop wallpaper is a concern for more and more of us.