I think it's a trend in recent years. Before in yaoi manga the seme always used to be older, now the uke being older is part of a counter-culture if that makes sense. Its also in general less frowned upon if the uke is older, even if its a predatory relationship. Not agreeing with that sentiment, but you have to admit people judge ukes less harshly in that aspect.
Yeah, I was kind of wondering if it was to help “balance” out the power dynamic between the couple
i don't actually care if both of them are already adults, be it a 10 year gap or whatever. what i don't like is the uke being/sleeping with/fucking with the children they 'raised.' that also includes tops who grow faster but still have a child's mentality. It doesn't sit right with me. ex. https://www.mangago.zone/read-manga/dawn_of_the_dragon/
It doesn’t bother me or anything, but I wonder if there is a reason why it seems like most manhwas have an older uke, or if it just happens to be coincidence. I’ve noticed like 90% of manhwas I’ve read, the uke is always older.