Online banking just isn't taking off in the US because people don't use it. They claim to be interested, enough people tell the bank they want it, and a bank puts a program in place that virtually nobody uses.
I spent 6 months working on a project that supported 6 major US financial institutions and their online banking, BofA being the largest customer, and one of the largest banking chains in America. They still had under 10% of their customer base using it with any regularity. The feature set they offered wasn't spectacular, but it was pretty decent, especially for the time when they were offering it.
As for the online banks, we had one of those on the project too, Wingspan to be exact. They had a kick ass system, well run on the back-end, pretty functional on the front end...they just couldn't make any money at it. Nobody wanted an online only bank, they just didn't trust the phenomena. The amusing part is that their worries were a self-fulfilling prophecy...nobody signed up, so the bank is up on the auction block from First USA.
I have a brick'n'mortar bank, nice little local place with only 5 branches. They have online banking, I use it regularly to transfer funds between accounts, keep track of what checks have cleared, etc. Then again, I'm also a geek, so it's more likely for me to use these features. My mom, who works with technology every day, doesn't use the features, she's been banking the same way for 30 years, and I can understand her desire not to change. She doesn't feel it'll save her any time...and at this point in the online offering world, she's probably right.
The banks, imho, need to take the first big step and make some truly great offers as far as features provided before people will start using it...yeah, it might be a losing money proposition at first, but as people come around to the idea it'll pay off in the end. THe big banks are the only ones who can afford to go first, but as they suceed the smaller banks will have to follow as people demand said feature sets.
"Its like someone opened my mouth and stuck a fistful of herbs in it." - Tamio Kageyama, Iron Chef 'Battle Eggplant'