There's a reason they do that: Most Japanese game developers games I know look really similar so they have to watermark their games otherwise it'd be so confusing deciding which game is which.
Also, it's not the real reason they do that, lol.
Japanese developers are still very strict and overprotective of their copyrights. They are generally not a fan of screenshot and video sharing and have overslept what a big, positive impact social media, streamers, reviewing sites and let's players have in marketing games world wide. These channels today sell the games. Western developers have long realized this and use it to their advantage. It's a hopeless endeavor anyway to completely protect your copyrights on today's internet.
Nintendo is an especially good example, because Nintendo of America and Nintendo of Japan are still so torn on this issue. Nintendo of America is pretty open and supportive of letting fans share their media, for example on Youtube in let's plays or reviews, they even partner up with Youtubers, Nintendo of Japan however is an absolute pain in the ass in this regard. They flag videos left, right and center that have the tiniest Nintendo game material in them. Many let's players and reviewers are really pissed off regarding that and it again was a big deal when the Switch was revealed.
That very different, antiquated view is the real reason, not because most Japanese games look the same.
