God may have given the land to Abraham and his descendants but the facts on the ground were probably a little different. It wasn't really theirs in anyone else's eyes until many years later when they waged war for it.
Jacob kept a flock of sheep which he probably herded over long distances. He didn't own land in the way a farmer might but it's possible he had a large grazing territory that he considered his. But when the famine came and he and his family left for greener pastures in Egypt, all that would have been lost to him. The only "treasures" he could bequeath to his sons were his flock, his servants/slaves, and whatever other possessions he had. That may have been no small potatoes for that time and place.
When Moses led the Israelites to Canaan 400 years later, they had to rest the land from the Canaanites. It was only then that the descendants of each of Jacob's sons, i.e., the 12 tribes, divided the land amongst themselves.