Because it's still using a server. large scale distributed resource abstracting server network (short lsd-rasn) or something along these lines would be more accurate.
Last time I checked (a couple of minutes ago), NONE of those "serverless" frameworks were truly serverless. Running your stuff or even your "functions" in the "cloud" is still running it on a server. Just because you do not know which specific server is running it at a given time does not make it "serverless". Why is it so hard to use the correct term?