is there a reason or do people just like him?

he has the most cost efficient partner with 2 attack for dual maps with Goomba. Yoshi is the 2nd best character to pick, as he has boo who also has 2 attack, but costs 3 coins per turn instead of the 2 that Goomba costs. Using any other character is gonna slow you down significantly,

What Fish said and because Luigi wins by doing nothing!