I was asked this to open the account (HSBC Premier US) - I just said I frequently visit the US and my main purpose for needing the account was to pay bills I have in the US. The trigger for asking was because I gave them a US phone number. They then said they needed more time to assess, and I didn't hear anything for a week or so until I got an email confirming the account was open.
HSBC Expat also has my AU address, they asked me for my tax file number, nothing else.
I've left the address in Australia for both. I also have a UK one, which has a UK address, they're all linked in the same Global View thing. For US, I'm 99% certain it's so they can establish whether you're liable to pay US taxes.
