Why do all manhwa seem to have a similar look?

Not all Chinese manhwa are the same. It could be that the ones you've come across happen to share some similarities, but there are many unique and different ones out there waiting to be discovered. Different artists and writers bring their own creativity and perspectives to the table.

It might be because many religions address common human concerns and questions about life, morality, and the afterlife, leading to some overlap in themes and stories.

Well, it's not really true that all have the same tech. Sometimes, limited imagination or a desire to stick to familiar concepts might make it seem so. But there are plenty of fantasy stories with innovative and diverse technological elements.

It's a common trope to add drama and character development. Without parents, characters often have to face challenges alone and grow stronger.

Maybe it's because there are certain popular tropes and trends that many authors follow. Or it could be that publishers are looking for familiar formulas that they think will sell well.

Often, it's due to limited perspectives and a narrow range of interests in the media. Maybe there's not enough exploration of different angles or underreported stories, leading to a perception of sameness.

Well, it might be because some common tropes and themes are often reused. Like the hero's journey or magical powers.

It might be for visual emphasis or to draw attention to specific elements within the panels.

It might be for better visual separation and to give a distinct break between panels, making the reading experience less cluttered.

It might be for artistic effect. The large borders can make the panels stand out and add to the visual appeal.