It is designed to be a user workstation. In some industries, such as pro audio, you often literally have a standard rack built into your desk where you can inst

It is designed to be a user workstation. In some industries, such as pro audio, you often literally have a standard rack built into your desk where you can install your desktop. In these environments, it is not uncommon for your desktop computer to be rack mounted. Since this is one of Apple's markets, it makes sense that they would cater to it. Dell also sells some desktops with rack mounting options for the same reason.