It’s less work for the citer, but that extra work helps guide against misinformation. In principle, you are only supposed to cite what you’ve actually read, so if someone has misdescribed the content of the citation, making the next citer check what the original text says helps catch the mistake.
And while citing the original is extra work for the citer, it’s less work for anyone who wants to track down and read the original citation.
It’s less work for the citer, but that extra work helps guide against misinformation. In principle, you are only supposed to cite what you’ve actually read, so if someone has misdescribed the content of the citation, making the next citer check what the original text says helps catch the mistake.
And while citing the original is extra work for the citer, it’s less work for anyone who wants to track down and read the original citation.