for shoulder health mainly...
If people worked the bicep curl as hard and the intensity of work was as hard as the other exercises then results would be different.
one set would be sufficient, two max, if you need to do three, you didn't work hard enough.
but the regular (heavy) bicep curl with a barbell should be in the top 10 list of exercises, this is not an "arms only" exercise, it's an "everything exercise" when it is done correctly...and heavy.
the leverage is so great that when in the half way position it works the back as much as a set of heavy stiff legged deadlifts and the downward pull on the shoulders works the entire shoulder girdle, if you could do a strict curl for bodyweight, that would be an amazing feat of strength, and one would look pretty muscular, Ive only seen a few do this; Grimek, Pearl and Reg Park.