In order to make the money cheaper to handle and harder to copy.
I can say with certainity that if I see any cash nowadays, I have to check the numbers in order to know their value (and yes, they are different colours and sizes for different values, but..). I am not even certain I have handled all the new versions. So, pretty much cashless for more than four years (while in Sweden).
I can see in person next year. Once a vaccine exists/is widely administered and I can travel again, Denmark/Sweden and either Norway or Finland are next on my list of places to visit.