Why does one not see the benefit of the morning and evening adhkar (remembrances) for their reciter, even though Allah and His Messenger have informed us of their benefit?

The remembrance of Allah is one of the greatest acts of closeness [to Him] and has immense effects. Ibn al-Qayyim mentioned over a hundred benefits for it. However, the effect of remembrance varies according to the faith of the one remembering and the presence of their heart. Supplications (du'a) and seeking refuge are like a weapon in the hand of its wielder; if one of the conditions is absent (the righteousness of the supplication, the presence of the heart, the absence of an impediment), then the effect will be diminished. So, whoever remembers Allah with a heedless heart, or is persistent in disobedience, may not experience the effect of remembrance. Sins prevent the occurrence of the effect of remembrance just as they prevent the answering of supplications. The Sacred Law does not contain anything indicating that one who remembers [Allah] will never be afflicted with problems. And Allah's promises of reward are a truth beyond doubt.