I've just taken a step that I've wanted to take for some time and completed the necessary forms to donate my body (when I die!) to medical science. My body isn't of particular interest, but the local university has a Department of Tissue and Anatomy which can use it for research and educational purposes. My wife has done the same. For us, this will be more beneficial than having our ashes scattered around a rose bush and, who knows, we may help a medical student become a great specialist.
When visiting a doctor, you rely on their training, competence and skill to diagnose your illness or operate on you, and training on rabbits isn't as precise as with the real thing. I'm not religious and don't believe that my body has an afterlife, so am quite content for doctors to use it and learn from it. There are, naturally, restrictions to donating to our university. A person has to be in the Alicante area and must not have any of a list of contagious diseases when they die. The university also has to have a need for the body at the time of death, so it could be rejected.
An additional factor of body donation is that there won't be a funeral and that has advantages for us. Firstly, as we live in Spain and our families live in England, America and Seychelles, attending a funeral would be a logistical and expensive process for them. We'd prefer to see our families while we're still alive and enjoy their company. The phrase 'celebrate life, not death' comes to mind. Secondly, the final cost is reduced; there is a charge for transporting the body to the university, but no other expenses such as for a service, coffin or cremation.
Following our action, we wrote to our families to explain our reasons and have received supportive and emotional replies that make me very proud of them. They understand our wishes and see it as selfless. Naturally, though, we hope that the university has to wait many more years before receiving us!