There could be all sorts of reasons.

Maybe they are surprised about how cheap or expensive it is to get a transaction through, and they want to show what mempool.space is estimating for fees currently. Or maybe they saw a block that was lottery-mined, that is, mined without being part of a mining pool, so that single miner gets the full block reward. Or maybe they are wanting to draw attention to how many blocks are mined by the same pools, many of which are just a front for AntPool.

All kinds of reasons folks might be posting images from mempool.space.