Why is ritual bathing (ghusl) after major ritual impurity (janabah) not invalidated by not performing the Asr prayer, even though abandoning prayer nullifies deeds, and ghusl is considered an act of worship?

The meaning of the invalidation (hubut) of the deeds of one who misses the Asr prayer is the loss of its reward and the forfeiture of its recompense, not the nullification of the act itself. The sin of missing the Asr prayer may invalidate good deeds, unless one repents. Al-Manawi and Al-Qari clarify that invalidation (hubut) here means the nullification or reduction of the reward for that day, and not the annulment of all previous good deeds, as complete invalidation is exclusive to apostasy. Therefore, a valid ghusl from janabah does not need to be repeated even if the Asr prayer was missed, but one must repent for missing the prayer.