Why are there so few posts on social media within the system?

Netizen A: If nothing happens, that's called life; if something happens, that's called evidence. When a few people gather, that's called an evidence chain.
Netizen B: I ride my bike for fitness during my break, posted on social media—over 50 kilometers. The boss replied below, "Looks like you're still not tired from work."
Netizen C: Really, I took leave to go home, then went out to play. My step count was still active, and the section chief asked me where I went.
Netizen D: In 2018, a new female colleague from out of town named "Queen of the Chess Table" joined our unit. Four minutes after joining the group, she received a call from the supervising leader.
Netizen E: I’ve experienced it myself—really love music festivals. Went to one on the weekend, wore a tank top, posted on social media, forgot to block them, and was reminded the next day, "Don’t post stuff like that."