Well, they're not films - they're advertisements. Different approaches work best for selling different projects. The Batman
folks want their established legion of fans to know that they're going to get what they've loved in the past in terms of the tone and characters; the ad is full of call-backs to past events and foreboding about darkness and desperation to come. These people also know that this minimalistic tease and viral ads have worked really well for them in the past.
people are saying "you haven't seen this before, not really, not like this."