Backup Walled

I understand the need for creating a new backup of the Walled when you change the password.

What I do not understand why a new backup is needed when you have done transactions. When you create a new Receiving address and you use it, it will be part of the blockchain will it not? So even if you loose the walled and put back an old backup that do not contain the receiving adresses you should be fine but not able to see the transaction in your walled but you balance should be ok, or am I wrong entirely?