They're artifacts from a more naive time on the internet. Meta has announced that they're going away next year on Feb. 10.

By February 10, 2026, the social media platform will discontinue its Like button and Share button for third-party websites. The social plugins currently allow users to “like” and comment on Facebook ...

So are external comment buttons, according to Meta. They’ll be discontinued on  February 10th, 2026, and starting on that date, they’ll render instead as a 0 x 0 pixel to prevent causing errors. [Link ...