Because upvotes also have the effect of elevating the visibility of content. Therefore, very very often, I upvote content specifically to promote it whether or not I “like” it. Sometimes because it feels important, sometimes to support and encourage someone brave enough to share something they created or love even if it doesn’t actually interest me at all.
Having my upvotes exposed to the public doesn’t give me an opportunity to explain why I chose to upvote that specific thing.
I only have WhatsApp because I have so many non-American friends ¯\_(ツ)_/¯
I dragged my mom and sister over to using it, and everyone has been warned that the second I see Meta trying to monetize it, I’m going to whine until they all move to Signal (which has pretty much identical functionality.)