This basic service is interesting for a number of uses especially for highly customized software which cannot work on PaaS or even cannot be fulfilled by SaaS. The disadvantage is that for this service the user must have appropriate experts for all lower level technologies like operating system and more. This kind of service offers a greater flexibility for any online software but also demands deeper a higher amount of technical skills in the different area.
Many IaaS providers now offer databases, messaging queues, and other services above the virtualization layer as well. Users get benefited with IaaS as they get bare metal infrastructure on top of which they can install any required platform.