Why we have to barter for a better deal

'Dear Virgin Media I wish to change to Talk Talk becasue they are £4 a month cheaper than you and give me free phone calls.'
'No problem Sir because you are a loyal customer, we can now offer yet another £5 off and give you bigger broadband; free calls and Tivo.'
'So thats a saving of at least £12 a month with so much more. Why do I have to threaten to leave to get a better deal?
'We don't know who is disatisfied and can't afford to ring everyone to tell them about our great deals. 
Utter Rubbish me thinks! Why not just give us all the best deal you can, and then we all know where we stand.