I’m not entirely sure. But my guess is that they want their friends to also experience and share the misery

Sometimes you recommend games to your friends because they’re bad games. There’s even content creators that explicitly look for ‘games so bad they’re good’.

Some games are so poorly designed or executed that the bugs and discontinuity become the fun, instead of just playing through them as designed. Horror games in particular just become funny when done poorly.

It definitely shows up if you actually go to the game’s store page. I’ve seen several friends’ negative reviews that way. I feel like it would be a positive for it to not show up on the activity page; if it’s bad, why would you want your make your friends aware of its existence? Better to leave your review in case any of them come across the game some other way.