Custom brushes seemed pointless, but a logo design shifted my view.
I used to think making custom brushes was too much work for little gain. Then, a logo needed a unique texture that default brushes couldn't do. I followed a guide and made a brush that nailed the effect. Now, I see how they can save time and add flair.
Oh man, custom brushes are a game changer. I always save mine in a separate "project brushes" folder so they don't clutter my main library. That way you can find them again fast if the client comes back for changes, which they always do. Saves so much headache later.