It’s not even real gratitude. It’s a phatic expression in the same sense as “what’s up” and “how are you?” not actually intending to be a serious question on what’s happening in their life. Expressions like these exist in every language to help with social interaction, in a sense it’s what gives language its human element, beyond just a medium of information transport. Hell even tons of animals have similar types of behaviours so it seems really weird to be so staunchly against this very common and basic kind of communication.

I fucking hate cars and I still wave drivers who stop simply because that’s the common etiquette. It takes nearly zero effort so it’s more of a why not do it type situation. I genuinely think it’s easier to just do it instead of getting worked up and opposing it because it’s such a simple thing that doesn’t have any negative side effects on you.