On Sat, 11 Nov 2006 17:47:31 +0000, Dave Newt wrote:

In fact, last time I did it in the opposite direction, and asked for
"BZ3 to Hertford East", the ticket seller at Tottenham Hale thought for
a millisecond, then asked me "How much do you normally pay for that
then?" I replied, "Oh, about £6.20 I think", and he issued me with an
LUL Extension ticket for £6.20, i.e. no destination of any sort printed
on it.

Is this because they don't know, or because it involves pressing too
many buttons, or is there actually a good reason for it?

It saves him having to look up the fare in a book.