Forks work loose over time. Place your finger in the gamp between headset and legshields, apply front brake and rock the scooter back and forth. If you feel any movement between headset and legshields, you need to to tighten forks. That said, the last time my forks were a bit loose, I couldn’t feel any movement there, I just felt vibration coming from the front.
If your rear shock, cones and engine mounts are in pristine condition, having too tight nuts possibly won’t increase vibration. But, it is conventional wisdom to tighten and then back off a quarter of a turn.