Why does God destroy all that we rely on?

Creator God sent famine even in a land flowing with milk and honey,

the land of Canaan (Deut. 6:3; 11:9; 26:8, 15, etc)

and destroyed all the supplies of food of Jacob and his children (Ps. 105:16).

Why did God do that?

Maybe God wants us to rely only on Him? 

In order to fulfill His promise to Abraham? (Gen. 12:7)

In order to move Jacob and his family to Egypt

and to make them multiply? (Exod. 1:7, 12, 20)

As a result, in order to deliver the Israelites from Egypt through Moses

and lead them to wilderness?

In order to lead them to the land of Canaan through Joshua after Moses’s death

and give the land to them?

What maybe God’s purpose of destroying all that we rely on

Through many different kind of “famine” in our lives?