I just bumped my "please add save and quit" thread on the Steam discussion forum. So far a handful of other people have written to agree, so it's obviously a common complaint, but the dev hasn't responded yet. If he doesn't respond soon, I'll see if I can find another way to ask him - someone mentioned Twitter, I think?
I'm sure he's somewhat overloaded with people contacting him right now, but I'm going to cross my fingers and hope this idea gets through. Save points in a modern game are just... Why would anyone ever think that's a good idea?
Save points in and of themselves are not a bad thing - it's the implementation that matters. Take a standard JRPG that uses save points; they're scattered around, usually right before a boss battle and in towns and so forth, and they serve as an ideal checkpoint in case a TPK occurs. You can run and use one at any time, and sometimes they even serve as a restoration point.
In Stardew Valley on the other hand...none of these apply. It's actually a potentially serious issue.