Today

Remember ye not the former things, neither consider the things of old.  
Behold, I will do a new thing;  now it shall spring forth;  shall ye not know it?  I will even make a way in the wilderness, and rivers in the desert.  Isaiah 40:18,19.

All of the miracles that the Gershonites were witness to had a purpose.  Apart from providing the needs of the people by daily providing mana and fresh water in a desert wilderness God was reprogramming them.
The Israelites were slaves in Egypt.  Four hundred years of service.  At the end of their stay in Egypt they were oppressed.  If you recall God hardened the heart of Pharoah that he would not let them go free.  The reason the passover is eaten with bitter herbs is to remind Israel of the bitterness of slavery.
After God got the Israelites out of Egypt He had to get Egypt out of them.  How did he do that?  By helping them to focus on where they were, and where they were headed, as opposed to where they had been.