My guess is that uploaders put those there so they don't get sniped,,, could be totally wrong but I honestly find it reassuring that someone with high quality translation will upload the following chapters(⸝⸝⸝´꒳`⸝⸝⸝)
Mangago uploads the chapter with a bot from another site like 1stkiss,bibimanga, etc and they upload the chapter just a few minutes after the chapter is released.
If you see the chapter from them they put watermarks on it, so the quality will be bad.
For us the uploader since we upload the series since the beginning, it's something troublesome to contact the admin to delete that bot/duplicate chapter,
Also as I know not all uploaders can upload fast like the bot, sometimes we are busy with RL stuff. That's why we put placeholder so we can edit the chapter later.
To the point, we just don't want bot chapter on our upload list since that troublesome to delete that chapter.
What's their use? I get my hopes up, only to see this