Poorly done electrical work is more common in American homes than most people realize. The electrical work in many old homes wasn't always according to code—some houses may even have been constructed before such codes existed. There was also a time when it was easy for service providers to get away with shortcuts.
The fact that you haven't had an incident so far doesn't mean that everything is okay. Things could be worsening behind the scenes, waiting for the right conditions for something to go wrong.
One of the main causes of electrical fires is ageing/faulty wiring. The kind of wires used in the past didn't have the best kind of insulation but often had rubber and fabric insulation. These types of insulating materials have been known to degrade with time, and this leaves the wires exposed.
If you're living in an old house (pre 70s), you should have it checked to ensure the types of wires used are not likely to degrade. There are other installation mistakes that may also have been made back in the day, e.g., running the wires through the wrong part of the home.
Sockets and Switches in the Wrong Location
It's also possible to find switches and sockets mounted in unsafe locations, especially in old homes. A common example is a switch inside the bathroom. A light switch in the bathroom can become wet in the humid conditions, leading to shorting or electrocution. Such switches need to be relocated to safe positions.
Low Current Rating
Wires, sockets, and extensions have a current rating or ampacity. This is the maximum amount of current they can safely handle. If forced to handle anything above the recommended rating, overheating is likely to take place.
An extension with a low rating may be easy to change. However, you may need to call an electrician if you're dealing with wires and sockets. You can get away with sockets and wires that have a low current rating for a long time if you've been using devices with low power consumption. However, this will change the moment you plug a device with a high current rating into that socket.
Main Switch Location
Your main switch should be located such that it is easy to reach if there is a reason to do so. However, the main switch in some houses is located in places that may not be easy to get to, e.g., the basement. This can be a problem.