Why to trade a class t4c for a t4cc crystal?

Tensio

I don’t understand why anybody would like to trade this. The other option a t4cc crystal for a specific one makes more sense

Paper_Tissue

In case you have any class in overflow, but are searching for another class.It's an opportunity to basically "reroll" what you get (albeit you can get the same catalyst back). But it's a 1:1 ratio, way better than the usual 3:1 trade-in.

Mirage_Turtle

And even in the off chance you re-roll the same one, you don't have to open the crystal right away. It's a good way to reset the expiration timer without having to rank up a champ you might not want.