Your title's a little misleading as the chart is specifically for "broadband penetration" (broadband subscribers per 100 residents) and not just Internet availability in general. Since there's no other details, I guess they're talking about anything that is non-dialup, specifically cable and DSL.

One possible explanation may be that with the proliferation of wireless LANs and WANs, there are many people all sharing a single broadband connection, making a broadband subscription unnecessary for many.

thanks, titles changed.