In the era of implant, to bring back complete denture sounds obsolete. However, there are still many reasons we need dentures; first, a patient can be medically compromised, uncontrolled diabetes, cardiac disease, radiation therapy osteoporosis patients who took Bisphosphate for long time are at risk of medication related osteonecrosis of jaw, or simply too afraid to undergo surgery. Second, a patient doesn’t have enough bone. Sure, you can do bone graft, right? But if you lost your teeth a long time ago. Most patients lack bone horizontally vertically. Bone graft is the best prognosis when it is surrounded by your own bone. (i.e. extraction socket) If you don’t any walls around your bones, the bone augmentation is extremely difficult if not impossible. Third, you may not simply afford implants financially.
In my experience; I've noticed various mini dentures. Probably, when patients starts to complain of sore spots, a dentist just grinds dentures away.
In dental school, we are taught there are 3 components in successful removable dentures; retention, support, and stability. For complete denture, you get retention from adhesion and cohesion so the contact area is larger you have more retentive denture. That’s why most people are happy with upper denture and lower denture is hard to be retentive. (Due to the tongue; which takes up space and moves denture around.) The key to success is to be experienced in this field of expertise.