You're not really wrong, but I understand that on Azure it's explicitly framed as a marketplace where you can purchase software to run on the computers you're r

You're not really wrong, but I understand that on Azure it's explicitly framed as a marketplace where you can purchase software to run on the computers you're renting. Much of that software, however, has no monetary cost. It's simply a quick and easy way to get the correct software from the correct vendor without going through the effort of preparing the disk images yourself.