I ride the bus and I can promise you I don't do it because of luxury. Even if that was true, it would only be true in North America. In the rest of the developed world, public transport extends out into rural areas.
I have spent a lot of time in Europe and, once you get away from population centers and even larger towns, public transit can get very hit or miss. OK, maybe there's technically a once or twice a day bus to that rural hamlet but lots of Europeans own cars and, while it's generally easier to get by without cars in areas of Europe, it's not like you can hop on public transportation everywhere.
It varies of course. Somewhere like Switzerland (as another poster notes) is generally easier to get off the beaten track by bus or train than a lot of coutries.
Are you by chance referring to Europe with this comment? I ask because Europe's idea of rural and North America's idea are quite different.