Of course student could take smaller class load. Student could take other unrelated classes and pick up a minor or a second major. Sometimes a plan for 3 yrs becomes 4, without a deliberate attempt to slow down. And remember too, that just based on numbers, only about 1/2 of freshmen return for soph yr. It would be awful to deliberately slow down for friends to catch up, then risk their dropping out!
My S started as soph, expected to be out in 3, didn’t work. He didn’t repeat or drop classes. Some courses were sequential and just weren’t available for him when it was ideal for him to take them. He picked up an unplanned minor.
Or maybe student would feel better about attending an unnecessary 4th year just to pay more tuition, housing, food, related costs? Just like a parent might pay for a kid’s summer camp- just so they get the experience? If that’s the case, offer school a higher tuition than they ask for, and graduate in 3 yrs. Then you can feel warm and fuzzy by paying for an unnecessary 4th yr, but move on to adulthood in 3. Friends are great, but college isn’t mainly a social club. It is an investment in one’s career and future. If the learning can be done in 3 yrs, then do it in 3 and get on to the next stage in life.