@Gargron
Your argument is valid but i think it seems not thought to the end.
AFAIK here on Mastodon IT IS welcomed to boost content from others - and sometimes you just want to add your own words to that.
May be to present this to your audience or to classify it or to show your (dis)approval.

I personally often want to boost a post, but at the end i do nothing because i don't like to present it "blank" (without my opinion).

Quoting does not necessarily have to be used in a negative sense!