I find it hard to believe completely because who doesn't like to make some more money even if it is not needed.
If you knew the exact sum you were going to loose gambling, and you are the type that they say " gambles for fun", will you find it fun loosing that money still? will you return another day in awareness of how much you will loose and still want to loose for fun?
Well if you don't make money you can't gamble for long but yeah tons of people do it for the adrenaline rush more than even the money part. It's an addiction to some, so it's probably a mixed bag of why people gamble. Not always for the money.