In Batman v. Superman, Affleck's Bruce Wayne has allowed Wayne Manor to fall into disrepair. The once proud mansion is now nothing more than a hollow shell of its former self. Instead, Bruce spends his time living in an elegant and contemporary lake house.
Recently on social media, Snyder explained why this decision was made:
"I think his father commissioned the lake house as a gift to his mother, a place built by her favorite architect, and she loved it. When Bruce turned 18, he moved in. He ordered Wayne Manor to be left to decompose."
Considering how hung up on his mother Bruce was in this film, it makes perfect sense that he would opt to live in one of her favorite places, rather than the gargantuan mansion.