With the exception of the latest embedded PC (identified as EPC-9611) manufactured by Protech systems, which has almost six serial ports, it is difficult to find popularly used PCs that have more than two serial ports.
While the lack of these ports is considered to be an anomaly by experts in technology, very little has been done to rectify the situation, even if it means simply adding a few more serial ports on the latest computers that have been released.
And if your line of work required you to use several serial ports, you would probably understand why devices such as the USB serial cable can make use of the several USB ports that are usually added in greater numbers to a PC as opposed to serial ports.
Once you have one of these simple devices in your possession, you can connect PDAs, printers, modems, digital cameras, etc., thanks to an increase in the number of serial ports available to you now.
Another interesting application is the USB extension cable, which might not necessarily deal with the lack of a serial port, but will help with your need to connect external devices to your computer that are spread over a distance.
In not having this device which uses a USB port to connect both devices, you can find yourself in a situation where you will have to move your computer or the external devices around every time you need to connect them together.
Last but not east, most users might need a serial port or two, but there are users who need different types of ports such as serial, parallel, PS/2, networking, Ethernet, and USB ports, and the perfect device that is already available is a docking station.
The best part of it all is that no matter which type of port or need you require, there are now several more devices that can help you to get what you need.