I think it needs to be this way in Bay's point of view to appeal to the audiences, he's most-likely targeted the film towards to the once teenage boys of 2007 that have become men or fathers over the years and Mark Wahlberg, the struggling father that's doing everything he can to provide for his family will make him relatable to the millions of younger fathers out there. You use a basic family element in your storyline to gather a wider audience base.
I'd love a Transformers movie where there is little to no human interaction, but it runs the risks (despite heaps of people saying they'd love just to see robots killing each other) of lacking the humanity element which draws audiences into it.