My co-authors don't want to help get our manuscripts published anymore. What should I do? Recently I've had three different sets of co-authors give up on the publication process.  Here are the three cases:


Publication was rejected on the basis that additional work was needed, amounting to repeating all the experiments.  One co-author has retired, another left academia, and a third just isn't interested in the field anymore (and has also left to work elsewhere).  To do all of the work myself seems a little unreasonable if after all that I'm still 3rd author.
Publication was desk rejected by multiple journals (5 so far) due to either being "too theoretical" or "too applied".  The other authors wanted to just turn it into a tech report, but after I started reformatting it, they decided they didn't care if it got published anymore due to the multiple rejections and wanting to move on to other things.  2nd author left our organization recently.
Publication has been written, but one of the authors refuses to move forward with the submission process because they are unsure if our conclusions are right.  Unless we have a "bullet proof" (their words) interpretation of our results, we can't submit.


I don't want to give up, but it's demotivating to have co-authors who don't care.  Is it worth it to keep fighting these battles all by myself if they still benefit?
Parts of your question are too circumstance-specific to really be answerable without more details, but a couple of the final points can be answered a bit.


  Is it worth it to keep fighting these battles all by myself if they still benefit?


You sound like you resent the fact that they still benefit.  That’s the wrong thing to be focusing on: the question is, do you (and your field!) benefit enough for it to be worth your time and energy pushing the work through to completion/publication?  If so, then do it — and if they benefit, then that’s a bonus, and with luck they’ll even be grateful to you for it later.

If you feel a third authorship isn’t worth the effort it’d take, but e.g. a first or second authorship would be, then discuss this with your co-workers as honestly as you can.  Say something like: “I think this work is worth the effort to get published, and I would be happy to do the main share of the work from here; but given the amount of work needed, I think in that case we should consider changing the author ordering to reflect it.  Would you be willing to consider that?”


  I don't want to give up, but it's demotivating to have co-authors who don't care.


It’s not necessarily that they “don’t care”.  They may feel as frustrated and torn as you — caring about the work and wanting to see it published, but feeling dispirited about the chances of that, and that at this point their time and energy are better spent on other things.