Psalm 78 is long list of how the people of Israel were given great signs of the presence and care of their God, but still turned away and forgot him. It shows how easy and natural it is for people to ignore all the evidence that God has given, and leave him out of their minds.
This psalm was written around 1000BC, and refers to incidents over the prior 400 years to illustrate all the signs and power that God had shown in the lives of their ancestors, but yet how they had still turned and forgotten.
Psalm 78:9: The children of Ephraim, being armed and carrying bows, Turned back in the day of battle. 10 They didn't keep God's covenant, And refused to walk in his law. 11 They forgot his doings, His wondrous works that he had shown them.
12 He did marvelous things in the sight of their fathers, In the land of Egypt, in the field of Zoan. 13 He split the sea, and caused them to pass through; He made the waters stand as a heap. 14 In the daytime he also led them with a cloud, And all night with a light of fire. 15 He split rocks in the wilderness, And gave them drink abundantly as out of the depths. 16 He brought streams also out of the rock, And caused waters to run down like rivers.
17 Yet they still went on to sin against him, To rebel against the Most High in the desert. WEB
They had seen truly wondrous things like the parting of the Red Sea as God led the people out of Egypt. But yet they soon acted as if it had never happened. They had taken it for granted that it was just part of life and of history.
In the modern context, the same basic human nature applies. Even though God has done so many things in the world, society will think they are just normal events, and don't even look for God in them. The very existence of animals, plants and life are taken for granted and assumed that they just happened.
God may as us, “How much evidence do you want? I've created your species, all the plants and animals, brought you rain, and even made available all sorts of minerals to play with. I've given a vast ecosystem with enough diversity and controlling organisms to keep the world stable. Then I've acted through my chosen nation, showing things you never thought possible, and had things written down it my book. Even I sent my son to speak directly on my behalf, and though you killed him, I raised him to life again. In recent times I've revealed to you many powers that you call medicine, electronics, chemistry... Just how much more do you really need to see?”
We may feel we need more evidence from God, but do we even recognise it for what it is when we see it?
Psalm 78:52: But he led forth his own people like sheep, And guided them in the wilderness like a flock. 53 He led them safely, so that they weren't afraid, But the sea overwhelmed their enemies. 54 He brought them to the border of his sanctuary, To this mountain, which his right hand had taken. 55 He also drove out the nations before them, Allotted them for an inheritance by line, And made the tribes of Israel to dwell in their tents.
56 Yet they tempted and rebelled against the Most High God, And didn't keep his testimonies; 57 But turned back, and dealt treacherously like their fathers. They were turned aside like a deceitful bow. WEB
If we have the mind to see it, there can be so much that tells us each day that God is. We may look for greater signs and proof, but given history, one must wonder that even if we were given more, would it really make any difference to us?
Related: Luke 16:19-31, Romans 1:16-21