Absolutely, but those are secondary markets for most American businesses because there are an abundance of issues with delivering any application to those areas. Whether its political, cultural, financial, etc. Priority for most businesses and website owners is to serve the people you know you can serve first, then work on supporting those other areas.

Twitter, like most companies, exists to make money. If you're busy shaving off every bit you can from your requests, you're spending a lot of money. You're also losing money because I'd expect you wouldn't be serving ads, etc. as well.

Most blogs that exist to make money aren't targeting those without good internet either, so I don't really see the problem.