When i was hospitalised for weeks (severe pancreatitis) and had to do low levels of exercise walking around the ward to get my strength back up, i thought that having light hospital aerobics exercise classes would be a great resource to have.

However you'd quickly run into problems with an already stretched hospital staff and budget having to then determine which patients are fit and well enough to participate and making sure the classes are tailored to their specific capabilities and restrictions. Also getting all the patients to the central location and then having staff on hand when things go wrong is another hurdle.