In UK Visa advertises contactless payments heavily, so do banks. They offer cashbacks on contactless payments or enter you in some kind of tombola. What benefit do VISA and the banks have when you pay contactless? I can see the theoretical advantage for small shops by being able to serve costumers quicker, but the banks?
Payment processors get a fee when you make a payment through their system. So by encouraging you to use their cards more, they make more money.
In the specific case of contactless cards, they see an opportunity to grow their market by displacing cash payments. So they're advertising it heavily to help that along.
At least in the US, one reason could be the "liability shift" that encourages adoption of chipped and contactless cards by shifting the fraud liability to the party that caused the transaction to not use chip-and-PIN / contactless payment: either the merchant (by not having a new compatible terminal) or the card issuer (by not providing the customer with a compatible card).
This means the issuers will try to replace old, magnetic-only cards as soon as possible once adoption of the liability shift is certain.