Bleach, Naruto, and One Piece keep readers engaged from chapter to chapter by building anticipation for what might happen in the following week’s installment. This helps explain the enormous amount of engagement whenever a discussion thread is created for the current chapter or the next one.
Frieren, by contrast, seems to be a different kind of story. Readers are invested less through constant hype and more through a balanced style of storytelling that encourages steady engagement with each monthly chapter, or it could have an erratic release schedule.
Edit: Frieren seems to be on indefinite hiatus?