Isn't the logic behind that is that TOR's original purpose was for secure, untraceable connections between military/intelligence personnel? If the traffic only composed of people working under the US government and their loved ones, it would be rather trivial to isolate the traffic and make a logical guess of who's talking to who. Opening it to the public was not something done as a honeypot for people to encounter, it is a requirement for the system to function as anonymous communication for all users.

As for why nodes are mostly hosted in 5 or 14 eye nations, consider where the funding for nodes is (and what would happen if you hosted one in a nation actively trying to strangle TOR traffic).

tbh i think that's more related to the fact that third worlders don't have the money to invest in what's essentially a hobby project that could get you into trouble.