I feel like its weird to call it a trope as if its abnormal. Wanting to return home to his friends and family is normal. Its not like he died and reincarnated and while he volunteered himself, he only did it so his sisters wouldn’t. He didn’t want to go to another world and he has a place to return to.
Agreed. The only times wanting to return to Earth is abnormal in an isekai is when the isekai'd person was depressed or suicidal or otherwise hated their life, had no real friends or family (if any at all), and all they have to look forward to is a dead-end job or forcing themselves to get through school, but they somehow
still want to return.
Like, in the moment, immediately after getting isekai'd, or maybe a day or two later as their new reality fully sinks in, I could understand even those people wanting to return; "better the devil you know", after all. But for it to keep coming up repeatedly as time goes is just ridiculous and only serves as a "hey, guys, remember that this is an isekai!" moment.
Luckily, I don't think I've read
too many like that; either that or I've purged them from my memory. But for the most parts, the ones who lack the things worth returning for generally let it drop quickly and for those few who bring it up again, it's generally done to illustrate how fucked up their mentality is.