I can think of two reasons: First, if the icons are indeed bitmaps, then a bitmap in PNG format is also going to be an embedded bitmap (<image>) in SVG, so it makes no difference and is easier to just use a set of PNG files at different resolutions. Second, support for PNG is built in to the Qt5Gui library, whereas SVG support requires an additional library (Qt5Svg). The purpose of examples is to teach, so simpler is better.