God set up a table of progression or priority. If there were no sons, the inheritance automatically went to the daughters. If there were no daughters, then the next step, then the third and fourth steps.
Why was God so concerned about land? There is a logical reason for it, as well as why He wanted the land to remain in the family. The principle, a very simple one, is shown in other parts of the Bible: Land is the source of wealth. If a person (male or female) has land, and he is able to work it, he will be able to produce a measure of income.
What a blessing that would be today, if every family owned land. This would solve one of our country's major problems! There would be almost no welfare because nobody would need to receive welfare from the State except in small amounts, since every family would be able to produce at least their own food (or some product by which they could buy food).
This principle within Israel kept a major welfare system from developing. In addition, there were the psychological benefits of owning land—because then a person has something tangible, something to which he can give himself, maintain, develop, use to create wealth and a sense of self-worth. Land gives a person a stake in the community, and with that comes a sense of responsibility to the entire community.