At some point, a knife is either owned by someone who doesn't care about it and is wearing it down by oversharpening or just using it no matter what, or a knife is owned by a caring owner who treats it with respect and gratitude and eventually it becomes a sort of "personal record" sort of thing. You get attached to the knife(or just still like how it works) and say "check it out, I'm gonna use up a whole freaking knife".

I think the third from the right looks like candidate #1 for oversharpened. The hourglass handle one looks as well cared for(or better) than the rest, so the handle was just scrubbed a lot more. Either a more fastidious chef, or maybe it was used to cut a lot of stinky fish or something, and required a little more elbow grease at the end of a shift.

Fun to think about. The beauty though is that you can sit and consider the personality and life of the owner of such an object, to the point that it becomes Art. Can't say that for most things in landfills.