Having been on the receiving end on that phrase numerous times, few genuinely felt sincere. It seems to have degenerated into a virtue signal more than anything else.

Yeah, maybe it's because I've got a lot of friends & coworkers that served or are active, but I just don't get the whole thanking thing. It's just another perfunctory statement.

I've kind of come around to the idea that asking some questions about the person's experience, and letting them tell some of their favorite stories is usually a better way of showing appreciation, even if it isn't openly stated. Everyone likes to be heard, and it's a rare veteran that doesn't have a bag of moving / funny stories to tell about being in the military, so everyone gets something out of it.

Only time I've ever said it was when I met a WW2 vet. Not that I don't support other vets it's just I feel that I actually had something to thank him for. I can't say my life would be all that different if we didn't invade Vietnam or Iraq. Everyone else I just buy them a beer and listen to their stories.

I remember seeing a lot of "support our troops: bring them home!" posters and bumper stickers in the mid 2000s.