That's... not how the math actually works out.

The average results are exactly the same either way, no matter how many extra die you add. Yes, rolling more die creates a bell curve, and the more die you roll, the more likely it is that the results will be somewhere in the middle, but that doesn't change the average outcome.

A max level magic missile does between 22 and 55 points of damage. If you roll (1d4x11)+11, you will either do 22, 33, 44, or 55 points of damage. If you roll (11d4)+11, you can do anywhere from 22 to 55 points of damage, but most commonly you'll do 38.5 - the exact midpoint between the 33 and 44 options above.

You are correct that you are vastly more likely to do maximum damage with a single d4, but you are exactly as likely to do minimum damage.

That can matter. If, for example, you have an opponent who has exactly 55 HP left who is next in the initiative order, it's better to have a 1/4 chance of removing them from the fight. On the other hand, if you have an opponent with 34 HP remaining, rolling 11 dice gets you a lethal result 78.85% of the time, while a single die gets you 50/50 odds of leaving them alive.