You can use it to prevent copy pasting of your wallet address especially when you are sending/receiving funds to your friend to make the transaction more easier. You can use it too if you have business or something that you will ask payment so that you can easily as payment by just scannin your QR code rather than sending your address to other user via social media app. It's not necessary to use it but it's just a tool to make a more convenient transaction. Just make sure that you are using a legit QR code generator website