Why You Need a Driver
Pins can't power motors; use a transistor or driver.
Pins Are Tiny
An Arduino pin can only push a few milliamps. That is plenty for an LED, but a motor wants far more current than a pin can ever supply. ⚡
What a Motor Demands
Even a small DC motor can pull hundreds of milliamps when starting. Connect it straight to a pin and you risk frying your board instantly.