At that point I candle and then assist any still living. Usually they have a reason for not getting out, like dried out or stuck in there wrong, I cannot believe the position some of them have ended up in. Silly things.
Dude your head is not supposed to be trapped between both legs... Let's undo that for ya...
Sometimes you find they didn't get out due to foot problems or their necks around funny, or just wedged in like a balloon in too small a space, or the shell was more porous than others and they're dried out.
Since I open all that don't hatch, I get to see some of the oddness. You also then find those that couldn't pip, pipped through their own yolksac, have really bad legs etc. It's good information to have because if those things PERSIST or increase in your lines - you need to know it.
I had one hen that kept laying too porous eggs despite supplements and a good feed. Had to cull her, most of her chicks needed help out from being too dry.
Just tossing unhatched eggs, especially without actually checking for life, loses you a lot of information if your flock is just getting started, and loses you some viable chicks as well.