In case you host your websites on a dedicated hosting machine, you would expect that they will perform very fast and that the access speed to them will depend solely on the Internet connection of the visitors. However, this won't be the case in the event that the hosting server has bad network connectivity or relies on a network card, which simply can't handle high volume of traffic. If this is the case, it shall take a while for your sites to load if many people open them at the same time or visitors might even see error messages. Because of that you might lose customers as probably many people won't return to your website in case they have experienced issues or slow loading speeds. This is the reason why you should pay attention to the network components of any new server which you get and not just to the main hardware which includes Processor, RAM or hard disk drive.