Just as web pages are adapted according to browser capabilities and existing mobile/desktop standards, sites can be adapted to very low bandwidth users. Not all of them, but many.
There's no point in Google Maps trying to send a VLB continuously updated set of map tiles, but an interface for the travel directions system can fit in a 4KB page - about 4 seconds of 9600bps usage. Get the weather, read the news, read and write blogs stripped of JavaScript and images, send and receive enough email to run your errands -- all these things are very high value for people who don't otherwise have connectivity, and very cheap to provide for them.
A few well designed websites are okay on 2G but certain not most.
(that's 0.5-1GB per day if used non-stop at maximum performance)