I'm playing White 2. Never hacked my game, 8 badges, traing my Pokemon to lv. 70 before enter elite 4
No reason, encounter rates are based on chance, where as a Mincinno has a common encounter rate there. You're just unlucky to say the least.
Chance of encountering Mincinno on Route 4 (in White 2): 25%
Why would it be strange for you to see Mincinno? You have a 1 in 4 chance of bumping into one. If you see more than that, then it's just that your game randomly decided to give you more Minccino encounters.