Because scaling up means you need to keep service costs down.

Whether the customer is on first name terms with the agent or the agent is on a different continent never seemed to make much difference to the info the engineer who actually sorts the fault got on his terminal when I was doing the job and from what I hear, things haven't got any better.

But I'm talking about the service given to ISP's end users .........

Before you commit to a contract you can't get out of I suggest you read

http://www.beta.bt.com/bta/forums/thread.jspa?threadID=2612

and

http://www.beta.bt.com/bta/forums/thread.jspa?threadID=2615

There you will find that they secretly conducted trials of the Phorm system last summer on "Kingston exchange" and consistently alleged that peoples browsers looking up dns.sysip.net must be a problem on their PC, that "Kingston exchange" had people in Brighton and wider afield affected (the suspicion is that it was Kingston RAS), that the description of how the system works given by BT does not match the description given by Phorm when asked the same question, that having faced a barrage of questions in the Q&A topic they started they have now withdrawn and answers are not forthcoming, etc. etc.