How to run Epic games through Steam

[WitzPrinz]

I have already read a thread on this but It didnt answer the question I was having hence me making another one. My specific question is: why cant I add my epic games games to my steam library
I know that when you try to do it, it shows you that some catastrophy has happend but I can open the games through double cklicking on it so why cant steam function the same way?