There are many lenders playing at "this level," presuming that by "this level" you're referring to the market for sovereign debt.
The area where there are only a handful of "players" is lending to countries that are very high credit risks. And for good reason. What rational investor would lend money to a party clearly unable to pay it back? None. That's a death wish.
Except of course when governments guarantee that party's credit for political reasons. Usually the arguments for such "support" include precepts that the free market leaves some nations behind, and so intervention is justified.
But the intervention, as we have seen quite often with the IMF itself, can do more harm than good.
And by the way, many "undeveloped" countries have respectable credit ratings (http://www.oecd.org/trade/xcred/cre-crc-current-english.pdf).