Is it really necessary to register your address?

Again, first I've heard of it. In any case, UK nationals do not register their addresses with any authorities. The only thing they have to do by law is provide details once a year for the Electoral Roll and are subject to a 5000 pound fine if they don't (well, it was last time I did it).

In the UK, the local Council sends each household an electoral registration form every year. You are legally required to return it. The fine for not doing so is up to £1,000. If you change address you have to fill in a rolling registration form to update the register, however you are not legally required to do this - it just means you can't vote until you are inevitably caught by the annual registration form again.
And to OP, we opened a joint deposit Euro account with Deutsche Bank in Berlin without providing a residents registration certificate. We just needed our passports and proof of residence in the UK in the form of a utilities bill.

This entire thread for one simple act jeees

Because it's in the script?

While it is true that there's no legal requirement to be registered to get a bank account, many banks will want to see a Meldebestätigung before opening your account.