My very first reason is because this Sony FE 24mm f1.4 GM lens is sharp across the whole frame. For people who love to "pixel peep" you will be able to notice the quality, time, effort and research that went into creating this wonderful lens. You would be hard press to find a better 24mm prime that is this sharp. Also, as an added benefit with the A7riii and A7riv when you use "crop mode" you get the benefit of two lenses of a 24mm and a 36mm all at once.
Depth of field. Bokeh.
The Sony FE 24mm f1.4 GM lens gives your images a very special bokeh look. It makes your subject appear to have a 3D pop. When looking at the image, it makes your background melt away like butter all while keeping your subject tac sharp.
For a 24mm prime the Sony FE 24mm f1.4 GM lens in light and compact. The versatility and build quality of this lens allows me to keep it on my A7Riv 90% of the time. This lens and camera combination allows me to agile in diverse situation where its event, wedding or street Photography.