The standard DM way of modifying these variables would be something like:
M.HP += 5
M.Gold += 5
Whereas, with accessors you'd define more functions and the same method would look like this:
HP = _HP
Gold = _Gold
Now, this looks like a waste of code, which was certainly what I thought when I first learned other languages (since I learned DM first), but in reality there are some benefits. Like having control over the possible values for variables. You could put an if statement in the setGold to check that Gold isn't negative.
Now, obviously, I think some people do use these sort of functions in DM, but I've never heard of someone defining accessors for virtually all of their variables. Would it be worth all the extra functions for the peace of mind that each variable isn't going to have some strange value?
Another random thought is that it might be useful if there was a way to call these functions generically, and I'm not sure that's possible. Is there really a programmatic way to call functions in DM? Assuming you kept to a naming convention for the accessors, otherwise it'd be next to impossible.