You can connect to the internet in your living room but you want to use it in your bedroom.
You want to have wireless WiFi access as close as possible to your laptop throughout the house.
You want to watch digital TV, via the internet, in your bedroom but the modem is connected in the living room.
Your children want to connect their games console to the internet from their bedroom.
You want to have your IP telephone and base unit close at hand no matter where you are in the house (in the garage when you are doing odd jobs, in the kitchen whilst you prepare a meal...).
You want to connect several pieces of equipment to the internet at once (computer, games console, IP telephone...) but you only have one electrical socket available.