A) I don't use it enough to make it worthwhile.

It would occasionally save you the difference between cash and Oyster
fares - makes sense if it is a frequent problem for you.


B) If you think I'm giving TfL my credit card details you're leaving
in a dream world

Any reasonable explanation why not?


C) None of this provides a good reason for paying by cash being twice
the price.

Yes, but the cost of paper tickets, handling, printing, proofing them
from fakes - all the extra costs that TfL needs to cover somehow. And
the less people use paper tickets, the more expensive it gets for
single ticket (economy of scale) and the bigger loss for TfL.