Which sounds like you are only impressed by damage dealers, and may very well be ignoring the tank/healer that made that KDA possible. So in a very real sense it is circular reasoning.
And how are you judging whether or not it is imminent? HP? Mana? CDs? Positioning? This is what I mean about your retreat not always being the correct answer. They may currently be at high HP, but their healer is completely out of mana, their tank is on full CD, and their damage dealers blew all of their heroics on me. Why retreat? There is almost nothing they can do to you at this point, unless your team also blew everything trying to save me. In addition, their bruiser may be wildly out of position, zoning your team away from my (soon-to-be) corpse, so a counter-kill could easily be possible.
To me, it sounds like you have a rather 2D perception of this game, where health bars are the only metric of success or failure.