Why not? Even if a PC is in an area of the world without any internet connection it may still be connected to a local area network and can still be attacked any number of ways including by infection from an MSBlaster-infected PC on the same LAN. It's not uncommon even for a PC which doesn't usually have an internet connection to be taken occasionally to somewhere which does have internet access such as an educational institution and directly connected to the internet from there in order to download updates, send emails, etc -- the only way of getting (occasional) internet access in some places.
Well, it's generally been my experience that in places where the population is too poor/too rural to afford Internet connections, they don't usually have computers at home either. Instead, they have net cafes, educational institutions, libraries, etc that have computers with a connection. People I know in those types of places make a trip to a net cafe or library occasionally to check their email or do other online business. Even if they did have their own computer, they certainly wouldn't carry it to the library to send their email.
Of course, I haven't been everywhere(not even close!), so maybe a place like you describe exists. If so, I'd genuinely like to hear where you have been that the people cannot afford an Internet connection but can afford to have a LAN full of PCs that can infect each other.