Motes of Light from Destiny 1 were used for infusion and you got 5 of them when you levelled up, so why not make it the same in Destiny 2?
Edit 1: Wow, weren’t expecting this to blow up this quickly, and also thanks for the gold kind stranger!
Edit 2: Some people were saying that 5 was too much for each level, so maybe lower it down to 4 for the first three levels of the week, and 2 for the rest of the levels, so that means that most people would get 12 cores a week, which to me is a good compromise.