In all levels in all relationship trust is an essential ingredient. The more significant the relationship the more important trust is. Lets take a friendship, someone who is more then an aquaintance to you, isn't it easier to care for that person when you know that person has a certain degree of trust for you? So is it surprising that the Bible says "The Lord is good a refuge in times of trouble He cares for those who trust in Him." Nahum 1:7 What about a girlfriend or boyfriend in a dating circumstance without trust it is very hard to move forward is it not? You feel betrayed, hurt, maybe angry if you feel the other does not trust you. So does it not seem natural that God would offer us promises like:

Jeremiah 17:7-8 "But blessed is the man who trusts in the Lord, whose confidence is in him. He will be like a tree planted by the water that sends out its roots by the stream. It does not fear when heat comes; its leaves are always green. It has no worries in a year of drought and never fails to bear fruit.

Jeremiah 39:18 "I will save you; you will not fall by the sword but will escape with your life because you trust in me, declares the Lord."

God wants us to trust him. He loves us so He offers us theses promises to us so we will trust Him. God wants to be in a real relationship with us. He gives us His Word, the Bible, His Love letter to us saying this is what I bring to the table, what he requires you bring to the table is your trust. This isn't something God just wishes for or hopes for make no mistake it is something He requires.
Why does God spend so much time making promises and instructing us to put our trust in Him. Well as I said before The more significant the relationship the more crucial the trust. We examined a romantic relationship, what about a parent / child or husband /wife relationship, what if there was no trust there. There would certainly be anger and damaged emotions especially if the untrusted party went out of there way to be trustworthy. How more so with God who created us. Who loved us so much that he gave his only Son that we may have eternal life. He gave us everything and yet we won't trust Him. If we held that up to any other relationship on Earth how would that stand. Lets look at how this makes God react. Numbers 20 God instructed Moses to speak to a rock in the desert to obtain water. Moses rebelled against God he did not trust God in what God had instructed him to do. Instead Moses struck twice his staff on the rock to obtain the water; although the water did pour from the rock this angered God. Because Moses did not trust and honor God he was not permitted to lead God's people into the promised land.
Now lets look how God reacts when we do trust in Him. In the book of Daniel during the reign of King Darius age 62, Daniel refused to give up worshiping God when the king made a decree that no other God or man except the king could be worshiped for 30 days. This was a plot by Daniel's enemy's who were jealous of him to overthrow him. Daniel was arrested while worshiping God and was mocked and thrown into a den of lions. The next day when the king went to see if Daniel had been eaten it was found that God shut the mouths of the lions and there was not a scratch on Daniel because Daniel had trusted in the Lord. Chronicles 5:20 Tells us "He answered their prayers, because they trusted in him."
Even Our Lord Jesus Christ compassionately urges us to trust in Him and the father. In John 14:1 He says "Do not let your hearts be troubled. Trust in God; trust also in me."
I'll close with this:

Proverbs 28:25 "A greedy man stirs up dissension, but he who trusts in the Lord will prosper"