Luk 18:8 …Nevertheless, when the Son of Man comes, will He really find faith on the earth?
The reason of God’s delay may be to increase our earnestness and grow or mature our faith. Many prayers are never answered because men faint at God’s delay. Faith misplaced robs prayers of its strength to persevere. Jesus calmed the storm (Luke 8:22-25) and immediately rebuked the disciples with a question, “…where is your faith?” They had some faith, but it was not ready at hand and therefore could not pray. “… for he who comes to God (in prayer) must believe that He is, and that He is a rewarder of those who diligently seek Him.” (Heb 11:6).
“…Weeping may endure for a night, but joy comes in the morning” (Psa 30:5). Joy in the morning is reserved for those like Jacob who have endured the night. That is the concern and question Jesus had, will His people have enduring faith until the end (second coming). The issue is not with God not acting but with believers not continuing to believe demonstrated by praying without losing heart.
If answers to certain prayers, which we have offered in an agony of tears, are slow in coming, we may be sure, either that the time is not ripe, or that He is going to do something better and should keep praying without losing heart, Heb 10:23 “Let us hold fast the confession of our hope without wavering, for He who promised is faithful.”