What about no-fault divorce? Why do couples still need to have grounds?

Some people confuse grounds with fault. Under no-fault, Rufus and Rhonda have grounds for divorce when they agree that they can no longer make their marriage work, yet neither Rufus nor Rhonda is at fault for this breakdown.

Ground for a divorce only refers to the reason for the divorce; fault refers to the fact that someone -- either Rufus or Rhonda or both -- did something wrong.

Back in the bad old days, one of the alienated spouses who wanted to part ways had to accuse the other of doing something wrong in order to get a divorce. That often made divorce court into a liar’s club and also demonstrated how skillfully otherwise law-abiding citizens could be at perjury, particularly when they were coached by lawyers who got rich doing it. That "something wrong" was often an affair, but it could also have been something else -- cruelty, abuse, abandonment.

In short, no longer do spouses have to accuse spouses of an egregious wrong; instead they must state that the marriage has suffered an irretrievable breakdown. This, however, still counts as a reason.
This is the ground for divorce, but no one is at fault.