First, height increase is entirely possible and anyone who says otherwise is just plain uninformed. By very physiological definition height increase is possible. It is possible for bones to increase in width(called appositional growth and involves increasing periosteal width or the deposit of new cortical bone by osteoblasts directly beneath the periosteum). Irregular bones like the spine don’t know the difference between width and height. Therefore since width increase in long bones is possible and width plus height is the same in short/irregular bones then height increase is possible.
Another myth is that the growth plates close! The growth plates do not close! They are just inactive. The hyaline cartilage resting zone does not die and ossify into bone because it already has an extracellular matrix. All you have to do to grow taller is to encourage the proliferation of mesenchymal stem cells, send them to the hyaline cartilage growth plate line, and then stimulate mesenchymal stem cell differentiation into chondrocytes.
Now, with all these facts why do people still proliferate the myth that height increase is not possible aside from limb lengthening surgery? Well, why doesn’t the government encourage bodybuilding? Big people are expensive and the government wants you to work, not try to get a better body. Why do you think the BMI doesn’t account for muscle mass? The government wants you to be as small as humanly possible! They certainly do not want you growing taller, that’s why you have to go to China to get the surgery performed.
Another reason is that stem cells are a relatively new science but stem cells can differentiate into almost any cell like osteoblasts, chondrocytes, and adipocytes. The former two being involved in height gain. Well fat can help you gain height too if you gain fat in your intervertebral discs or on the top of your head.
So you can see that height increase is not only possible, it’s almost an inevitability that height increase methods will soon develop. It’s a lot easier to develop a non-surgical method of height increase then a non-surgical means of curing scoliosis for example.