Old but gold (and still relevant), especially for those who do not secure their online accounts.
Source: Why a PIN is better than a password (Windows 10)
PIN is tied to the device
One important difference between a password and a Hello PIN is that the PIN is tied to the specific device on which it was set up. That PIN is useless to anyone without that specific hardware. Someone who steals your password can sign in to your account from anywhere, but if they steal your PIN, they'd have to steal your physical device too!
Even you can't use that PIN anywhere except on that specific device. If you want to sign in on multiple devices, you have to set up Hello on each device.
Source: Why a PIN is better than a password (Windows 10)