The text simply say's it's cheaper, but the amount saved is not mentioned. This can be a big factor in changing people's behaviors. I may choose to shop at a local market for convenience, or fly a specific airline to get airline miles. In both cases, I know that I did not pay the absolute rock bottom price, but that the difference is small enough to not deter my loyalty.
Later in the article an example is given: "...Paddington to Canary Wharf would cost £6.70 if buying a paper ticket but £2.80 if using contactless payments" I am unsure how random that example is, but if typical, that is a massive 60% discount. Sharing that sort of precise information would certainly change habits of even the most loyal of paper customers.
It is of course far simpler (and cheaper) from a software design perspective to have the generic message, and perhaps it is all that could be accomplished in the timeframe allotted to the effort, and I understand that. But I do hope that more precise messaging is provided in the future so that we can revisit this discussion and review the results.