Because currently, it seems like the only thing it’s recording are downvotes. Meanwhile upvotes are completely ignored, leading to pretty much every profile I see having a negative reputation.
Also, I have a very fragile ego and my -6 reputation hurts a bit.
As @HidingCat said it’s to increase compatibility with the other app. If I’m following your Kbin account from my Mastodon one, when you boost something I’ll see it pop up on my feed. I’d be in favour of keeping it but changing the label to something like “boost to fediverse” or “share with followers”, or even just “share”.
“share” is obvious in what it does, and efficient in terms of using space on the website. I like it.