It’s not usually necessary for beer. Wort has a lot of nutrients in it already and is a good environment for beer yeast. Adding nutrients and energizer is more important in mead and cider, and is especially important in more neutral fermentations like hard seltzer, which needs all the help it can get. If you’re brewing a big beer, not using a starter, or are just worried about it, you can add some at the end of the boil. It doesn’t hurt and I’ve always had healthy ferments when using nutrients.