I think he's tough to main by himself, you need a secondary IMO. There's certain characters I hate playing as Wario. I decided to use Wario as my go to secondary basically because he covers the Sonic and Zero Suit matchups really well that my main, Dedede, is awful against. Likewise Dedede tends to be awesome at matchups Wario isn't good at. I think it is important to learn a secondary if you main him because he does have matchups that are a pain.
But one of the biggest reasons to main Wario is nobody plays him, so you can really fool some people. Very few tournament players have a lot of experience against good Wario mains. Wario plays so entirely different from the rest of the cast. Many people have absolutely no clue how to deal with the bike and bite mindgames. Matchup experience is in my opinion more important than where the characters stand on the tier list. And frankly, Wario is pretty darn high on the tier list anyway.
And there's very few things as satisfying as landing a waft to seal a game. Also Wario is such a troll. Farts of death, infinite bikes come out of his ass, bite, what more could you want in a character? :D