Babies are born myopic and later improve their visual acuity so why can't myopia in adults be improved in a similar way?

A babies myopia relates to the shape of their smaller eyeball & the fact that shorter/smaller eye sends visual light to focus on a point behind the retina. With growth, the sharp focus moves forward to the actual retina as they get older & achieve their natural eyesight. Adult eyes have a fixed focal point that will not change. Eyeglasses or Lasik can change the focal point to correct vision.