Medicine isn't the only way to cure diseases and exercising proves many benefits. Medicine can't cure obesity but exercising definitely can help. In order to create a cure for all the diseases, it would take scientists far more years than the average life span so exercising is the best option. Exercising helps with not only your physical health, but your mental health so it has more benefits than medicine can have. So, unless you plan to wait through a bunch of diseases, exercising can be one of your best options.
(Sorry if it's bad, I was putting things off the top of my head)