Not a gimmick and vastly more secure than that debit/credit card in your wallet.
Google Pay (Android Pay) uses a generated 1 time card number that is matched to your real card details by the payment processing company (Visa/Mastercard) and then discarded.
If I lose my phone, I can remote wipe it, Can I do this same thing when I discover my credit/debit card missing? Your plastic card is however ripe for skimming.
It's therefore no surprise that banks limit card tap and pay transactions to £30, but don't impose that limit for GooglePlay tap and pay transactions (as long as you have some form of password/pin/fingerprint lock screen)... Go figure...
Good luck Luddite. I wish you all the best,. Don't forget the tinfoil hat.