How and why are objects on the screen are identified when clicked upon?

[c64zottel]

There are several ways in 3D programming to identify which object has received a mouse click, which may be put into two categories: Calculate via raycast or color picking from a second framebuffer.

It seems that egui uses a form of the former solution. I would like to ask why this method was chosen - is there some deeper reasoning behind or was it randomly selected?

Thank you.