Specialization? Niche? The A-10 kills massive amounts of stuff, up close and personal, takes heaps of damage that would send fancier planes crying to mommy and helps your mud mover do what war is all about: taking and defending ground. It can operate from improvised airstrips, fly treetop level and gives a new meaning to "cross my heart and hope to die" (if you didn't get it, imagine seeing it from below).
It's what a combat aircraft is meant to be. Nothing more and nothing less. Sure, it can't put a bomb into your enemy's HQ the other side of the world, but that's what DHL is for...