God knows that we are a forgetful people. It is interesting to notice as you read the scriptures, how many times God gave his people reminders of important things. When you look at the Noahic flood for example, after the flood a rainbow is given as a promise that the world was not going to be destroyed through water again. But it was also, in a way, given as a reminder of God's love and care for his creation.
When God gave his law through Moses to the Israelites, He gave them a very strong warning. “Only take care, and keep your soul diligently, lest you forget the things that your eyes have seen, and lest they depart from your heart all the days of your life. Make them known to your children and your children's children— how on the day that you stood before the Lord your God at Horeb, the Lord said to me, Gather the people to me, that I may let them hear my words, so that they may learn to fear me all the days that they live on the earth, and that they may teach their children so" (Deuteronomy 4:9-10). Also Deuteronomy 4:23 reads, "Take care, lest you forget the covenant of the Lord your God, which he made with you, and make a carved image, the form of anything that the Lord your God has forbidden you."
He reiterated this sentiment in Deuteronomy 6:10-12, “And when the Lord your God brings you into the land that he swore to your fathers, to Abraham, to Isaac, and to Jacob, to give you—with great and good cities that you did not build, and houses full of all good things that you did not fill, and cisterns that you did not dig, and vineyards and olive trees that you did not plant—and when you eat and are full, then take care lest you forget the Lord, who brought you out of the land of Egypt, out of the house of slavery."
There are many more examples of God doing things and saying things to remind the people to keep reminding themselves. The Christian is given one great reminder. At the last passover meal that Jesus ate with His disciples, He began a memorial involving unleavened bread and fruit of the vine which allowed them to remember Him. 1 Corinthians 11:24b reads, "...Do this in remembrance of me". For Jesus to have said that, implies that He felt like if there was no memorial for Him done weekly, people may have forgotten. What better reminder is there for us to think about the sinless Son of Man giving His life for our sins.
When you look at how God communicates to His creation, He knows we are forgetful people. He cares about us and wants us to be mindful of the important things.