Changing the MAC is a matter of privacy. There are different reasons why it is recommended to change the MAC of your device. One of them is if you are going to connect to a public network where there are more users connected.
Remember that the MAC is an identification of the physical hardware, of your network card and is unique to your computer.
It is always recommended, for security, to change the MAC when you connect to a public Wi-Fi network or a VPN.