While there are plenty of guys who try to get drunk for the mitzvah, there are also a lot of yeshiva bum ois vorfs who are just taking advantage of another opportunity to get drunk.
Let’s put it this way: Most people who get stone drunk on Simchas Torah or Purim night, and most people who get drunk on liquor on Purim, are probably not drinking on Purim b’ikkar for the mitzvah. One should be dan l’kaf zechus on an individual basis, but it is pretty obvious that there are plenty of idiots out there.