Why do we not celebrate when the child stops nursing (as Avraham celebrated Yitzchak reaching 24 months, Bereishis 21:8)? Especially those who anyway מניחין דברי תורה ועושין כל ימיהם כחגים. (Chana and Shmuel may be a seudah shel mitzvah due to the Neder, and likewise other examples.)
Maybe it’s a sign of health, so it’s less relevant?