Most of our lower level players only appear in guild chat to ask if anyone can loan or donate some items (or for GQ help).
They stay a little while, say hello and then generally are gone once again after 5 minutes or so. We hope that, once they become familiar with the more chatty members, they might become more active in guild chat too.
With guild bank, presuming any can afford it, this interaction is likely to diminish if not disappear entirely.
As I see it, the only benefit of guild bank is, it allows a member to transfer resources while another is not online. Someone could wake at 6am and borrow/take a few k marble or whatever rather than waiting for others to wake at 7am or whenever.
Not really worth the 3k coins and island space in my opinion.
If we could roll back the clock, that developer or group of developers could have spent that time doing something useful instead.