I'm definitely still significantly under sixty-five and I use a smartwatch to pay for stuff. That said, at lunch the other day, I did this and my colleague, an owner of such a watch exclaimed "oh, I didn't know you could do that." Quite possibly people are just using them to tell the time. Anyone under the age of 25 do tend to just use their phones on the basis they never actually leave their hands anyway. Some of them wear chunky watches as accessories. They probably aren't using them to tell the time. They may be surprised to know this is a function of a wristwatch. No one tell them that actual cameras are available.
It won't be the first time someone is amazed when I pay by watch that I have a 'chip' because the watch is hidden under my jumper. Anyway, it's more practical than faffing around for cards or my phone. I also use it to tell the time (it's generally handy, when it's buried away under jackets and stuff, especially when cycling home, to demand that Siri tell me the time, which she duly does).