Crosspost, acecow style
Warning: Spoiler! (Click to show)
I'd wear this.
Because it's not a MC blazer. Biker jackets like the one he's wearing were designed to be worn on bikes, which meant that the sleeves were cut longer to protect your wrists from the wind while gripping handlebars. Most modern biker-style jackets are still cut that way even if they're no longer intended to protect you while riding.
tl;dr because it looks cool