Thanks for the reply and the information, I guess that makes sense.
I did do some more googling though, and found this site 'letshackarcadegames.com' which seems to have a lot of information on the subject, including information on how to (start) using the debugger to reverse engineer a game. The last article in the series seems to be from September 2015 though, so I guess it's no longer updated.
Introducing the MAME Debugger
Thanks again for the help.