I have a friend whose wife is a branch manager for one of the larger bank brands and he swears that the banking industry is on the verge of going fully automated where dealing directly with a teller will be a premium service that will cost extra.....
You also have to consider how the banking industry has changed....[they] had to have that large prominent building and an image in downtowns to not only accommodate their customers, but also to house all of their support staff and other operations....
I think if you are in agreement with your friend's wife feelings about the banking industry, I am with you and them. It is increasingly becoming a robotic and automated world. FW Business Press has a story that even oil rig workers are being replaced by automation.
As for how the banking industry has changed, I would agree that branch banking has been a lot to do with ending the consolidation of personnel under one roof. It probably always has been that banks occupied the street level of a building plus 2-4 floors of a skyscraper; and that the bank used its surplus office space for multi levels of tenancy. Assuming that this has been the typical way that office space is filled in a office tower, I would also assume that a bank would also see the economic return of a multi-story tower as both a place to do business and a source of income.
Regarding, 640 Taylor (Frost Bank), a larger visual than actual presence in Downtown is likely the reason why Frost Bank for quick to have its brand displayed at the top of 640 Taylor.
That the bank proposed for 7th @ Summit is building a two story structure just to meet its needs and nothing else, then from an economic argument, if building was larger (tall) there would be a stream of income even as the bank's own operations and staffing downsizes as a result of automation. A tower would have made for perfectly sound economic course of action as well as an important marketing effort for this bank once the original costs have been made.
This seems as a missed opportunity at a reasonably prominent site.