1. His name is similar to mine and somewhat close to darien.
2. His bleeding passive is really annoying to calculate when laning against.
3. His Q is an effective wave clear, harass, and is not effected by attack speed debuffs by doing more sustained damage with his kit, adds a stack of bleed.
4. His story is even badass, he kills his own captain in his first battle to lead the troops to victory.
5. His W is needed for every brusier, an auto attack speed canceler. Not only does it do bonus damage but it slows and adds a stack of bleed.
6. His E creates opportunities to initiate, catch and kill.
7. DUNKS his ult creates pentakill opportunities
8. His burst is amazing for an AD brusier.
9. Spamming his dance is funny. His laugh is funny. His taunt is funny. his joke sucks though imo. it makes him look like a *joke*. hohoho..... ok nvm.
10. He has natural built in armor pen, so you can just build ad, or tank and still do a lot of damage in team fights.
Of course there are reasons not to play him.
1. If you build him wrong his late game sucks.
2. Hexdrinker is a core item and it is bad late game.
3. Phage gets stuck being a phage for the longest time. (and now phage costs more)
4. He doesn't last as long as other brusiers and gets rolled by champions outside his e range if you get kited properly.
5. You can't deal with poke very well 0 sustain, you're forced to flash apprehend if you have no initiate.
Edits: Added a math section between triforce and BT (last chapter, user full credit)