I think so much is dependent on the school and the kids’ desires. My parents and my boyfriend (now DH) parents met at our graduation. The graduation ceremony was on Sunday morning, but Saturday had ample opportunities to socialize. The school had some open house type events and then held a tent party that night. DH and I organized a BBQ for our friends and their parents.
Did DS go to this college too? Do they have mutual friends who might want to hang out for part of the weekend? I can definitely see opportunities for low key socializing outside of the formal ceremony.
On the other hand, at some larger schools, it might just be one humongous ceremony and no real way to meet up with friends.