Why might a system not be 100% efficient?

A system may not be 100% efficient due to a variety of reasons. For example, there may be energy losses due to friction and other sources of resistance, which reduce the energy available for useful work. Additionally, the system may have components that are not functioning optimally, or it may have inadequate resources to complete the task at hand. In some cases, the workflow itself may be inefficient, with steps or processes that take longer than necessary. Finally, the system may not be designed or powered with the utmost efficiency, meaning that it does not make the most of the available energy or resources.