My logic behind that is that they should be owned by, and the ATCs work for, the aerodrome operator.
So who at MNG is going to pay for a tower? They don't own the navaids, so can't charge for the overhead training, and there wouldn't be enough landings to cover the infrastructure costs. if you make it too expensive and restrictive, they'll just go somewhere else.
At what traffic level does pilot separation by radio become impossible and unsafe? I think we found that out at Mangalore
How many aircraft were on frequency at MNG? There's no mention of frequency congestion. Both pilots got traffic on each other. They didn't talk to each other. So the answer to what traffic level is dangerous - Two.