Heat is one of the biggest factors that can negatively affect a PC. It can cause a computer to run slower, damage components, and in the case of laptops, shorten battery life.
Dust can also cause heat buildup. If you put a computer tower on the ground, it won't be long before it has absorbed a significant load of dust, sand, hair, etc. Laptops are even more susceptible to dust.
Cables can come loose very easily, both inside and outside of the computer case. If any computer experiences hardware problems, it's worth checking that all internal cables are properly connected to the motherboard.
In addition to protecting yourself against power surges, you should also protect yourself against power outages. In most cases, a remorseful power outage can result in data loss, but hard drives and solid-state drives could also suffer permanent hardware damage.