When thinking of that as not the default, in a cultural comparison, “how are analogous-role conversational elements expressed differently” is the most salient. So compared to a culture in which you don't ask that so cheerily, obligatorily, without-‘really’-meaning, yes, it totally is fluffy.
(Speaking as someone who's theoretically American but culturally ambiguous, who's recently been suggested by someone reviewing my social skills in a professional capacity to inject more low-content happy-mood pleasantries into my conversation—they may have actually used the word “American” in the process, and I hardly disagree with the connection. Of course, that's papering over a lot of intra-American variation too.)
It's a deliberate short circuit to a real human problem - the problem of two compatible people (whether friends or lovers) being artificially delayed on connecting with each other because of "customarily enforced" protocol on how quickly they're allowed to be familiar. That problem is bad enough that it's a staple trope in rom-coms and buddy cop films - and it frequently leads to tragedy because of how short life is, and how opportunities don't last.
It feels like there are a lot of people in the american cultural milieu who've picked this up from other groups of americans (america's a huge country with tons of different culture groups), but … are missing the absolutely CRITICAL ingredient of taking it at face value.
It is exactly what it looks like; it's not facetious, it's not fake, and anyone who treats it like that is kinda cargo-culting it.
That's a gross oversimplification; the particular question used as an example may or may not be a genuine question and whether it is or isn't varies from person to person and, even for the same person asking, often by who they are asking and the context.
Treating it as a non-question to be blown off with a ritual “fine” can be anywhere from the correct formulaic response to an acceptable way of indicating you don't really want to discuss specifics to a significant insult.
For contrast, in Northern Europe a cashier would greet you with the local version of "Hi", "Hello" or "Good morning". And them not verbally greeting you would be socially acceptable too!