The simple flash of the brand name and product is all that the advertiser is after, usually to reinforce a wider marketing campaign. Bus advertising is usually short and humorous, and for obvious reasons contains no animation. There are already web banner marketing strategies that make sense. Content based banners are usually more effective, for example advertising mail probes on a virus information web site. Targeting the audience is more possible on the web than on the side of the bus.
Web banners expect to capture an audience with ineffective methods to produce unrealistic results.
The click-through focus should be alleviated. Traditional advertising has always recognised the fact that people simply do not see an ad and then go out and buy the product. Why it's expected on the web is an unknown. Banners that are part of an overall marketing strategy are. Much like bus banners, people will simply ignore web banners, or register them subconsciously.