Totally a valid reason to play. That's what is so great about games like this there's something for everybody. I pretty much play to see how many hundreds of millions of Gil I can make even when I have nothing in mind to ever really spend it on. It's just what I find fun. I like doing dungeons and quests and crafting too but primarily I try to make crap-tons of Gil =D

Just play however you want there's no *wrong* way to play except, as others have stated, if you're goal is simply to harass other players. Sometimes it *is* fun to run through a crowded area slapping everybody though but that doesn't really hinder anybody's gameplay. It's just funny!