On graphic/print design your final medium is paper which has no problem on rendering. When you flip the page all the graphics are on the paper already but think about digital interfaces. Your final environment will be a mobile device or a web browser so you need to make it load and work fast. Otherwise, you'll lose customer each milisecond. So graphics designers need to learn which renders faster, when to chose a svg or raster image, how to optimize an image, how much time does it take to load a font family and which file format is supported etc.
Optimization.
On graphic/print design your final medium is paper which has no problem on rendering. When you flip the page all the graphics are on the paper already but think about digital interfaces. Your final environment will be a mobile device or a web browser so you need to make it load and work fast. Otherwise, you'll lose customer each milisecond. So graphics designers need to learn which renders faster, when to chose a svg or raster image, how to optimize an image, how much time does it take to load a font family and which file format is supported etc.