So that custom inventory views that extend InventoryView can override it to set whatever title they wish; if you're extending InventoryView, there's no other way to specify a title.

Of course, I could've added an openInventory method that takes an InventoryView and a title, but this seemed better to me.

As for why you'd want to extend InventoryView, I think a significant use case would be to show an inventory view that has nothing to do with the player's inventory.