Regular hardware diagnostic is a crucial part of computer maintenance preventing catastrophic failure and potential data loss. For example harddrives have a built in programme monitoring their performance and logging every error they encounter. Reading these errors regulalrly can be an indicator if a harddrive is in an early stage of a failure due to wearout. Replacing a harddrive in this stage is far less cheaper and easier then recovering data fom an inaccessible HDD.
Many times the blue screen of death or other software issues are caused by faulty computer components like the mainbord, RAM or the processor.
Another common issue especially in laptops are the clogged fans preventing the heat to exit, causing the processor to overheat until the thermal sensor shuts it down.