MQTT configuration user

MQTT Installation

I saw a couple of online guides for installing the MQTT Broker on HA... but with the latest updates something has changed and I don't understand what the correct way to install is.

1- I first created a "user" for MQTT...

2- than, from Application, I installed the MQTT broker.

3- after installing it... from the MQTT Broker settings someone says to go to "Configuration" and add the user we previously created in Home Assistant (point 1) to LOGIN.
In other guides online this part is not present...

4- "Device and Services" ad the integration... after installing it, go to reconfiguration and add the User and PWR previously used for MQTT broker.

I don't understand why at point (4) someone enters the credentials of the new user... others don't.

Which is correct?

EDIT: I understand that it is recommended to create a user and log in with that, but I don't understand why or what the advantage is.