Why does Allah repeatedly warn against the Fire, does it not contradict the attribute of divine mercy?

A mother exhausts her children with her numerous warnings whenever they travel or go to work to be careful to themselves in their each commute. Is she considered a cruel mother? This is a clear misjudgment to consider mercy cruelty. Allah alerts His slaves and warns them out of His mercy. He guides them to the way of salvation and promises to replace their misdeeds with good deeds when they repent to Him.

{Except those who repent and believe, and do righteous deeds; for them Allah will change their evil deeds into good deeds, for Allah is All-Forgiving, Most Merciful.} [314] Surat al-Furqān: 70.

Why have we not wondered about the greatness of the reward and the bliss in the eternal gardens of Paradise in return for a few acts of obedience?

{But whoever believes in Allah and does righteous deeds, He will absolve them of their bad deeds and will admit them to gardens under which rivers flow, abiding therein forever. That is the supreme triumph.} [315] Surat at-Taghābun: 9.