Because if you do, you could be in breach of Davros' terms and conditions and therefore require termination and extermination.
This is the kind of letter you might get from the BT Cybermen... or from its chief Dalek Davros. The only bit we made up was the Davros bit at the end.
Dear Customer,
We refer to our previous email regarding your BTopenworld account.
Our records show that your account continues to be connected for long periods of time - typically 12 hours or more in a day. Unfortunately, as we informed you in our earlier email, this is a breach of our Terms & Conditions. To review these, please go to http://www.btopenworld.com/helpnb/terms
We are sorry to tell you that your account will be terminated from 2nd July 2002, in accordance with our Terms & Conditions (paragraph14 (b)).
If you use a BTopenworld for BT Surf Package please note that only your BTopenworld for BT Surf Package will be terminated. If you no longer need your separate BT Surf Package, you should cancel it by calling BT Retail on 150 using a BT line.
An 'always on' internet connection may better suit your needs and you may wish to consider high speed BTopenworld Broadband Plug & Go. It's up to ten times faster than a standard modem and uses your existing BT line without affecting your voice calls. Once set up, there are no extra charges above the monthly rental fee. To find out more and check broadband availability in your area, please go to http://www.btopenworld.com/broadband
If you have any questions about your account termination, please contact the BTopenworld team at http://www.btopenworld.com/helpnb.
When contacting the BTopenworld team, please quote your email address and reference number Axxxx.
Yours sincerely,
Davros
Leader of the Universe
BTopenworld team
www.btopenworld.com