He promised to come back; why doesn't He come?"

Thoughtful Christians of all churches have one common question: "What is Jesus Christ doing? He promised to come back; why doesn't He come?"
Yes, He promised, "As the lightning ... so shall the coming of the Son of man be. ... But of that day and hour knoweth no man. ... As the days of Noah were, so shall also the coming of the Son of man be. ... They ... knew not until the flood came, and took them all away; so shall also the coming of the Son of man be" (Matt. 24:27-39). The angels promised the disciples, "This same Jesus, which is taken up from you into heaven, shall so come in like manner" (Acts 1:11). That literal, personal return of Christ has not yet taken place.
The only answer as to why He hasn't come back yet that can possibly make sense is that His people are not yet ready for Him to come. The harvest is not yet ripe (see Mark 4:26-29). And what special ministry can make a people to be ready? Only the ministry of Christ as High Priest in the heavenly sanctuary (see Heb. 8-10). There was an earthly high priest in the ancient sanctuary--so there is a divine High Priest in the heavenly; there was an earthly lamb offered in the ancient sanctuary--Christ is the "Lamb of God who takes away the sin of the world" (John 1:29). As there was an annual day of atonement in the earthly sanctuary, so there is a cosmic Day of Atonement in the heavenly when the High Priest ministers in the Most Holy Apartment, the second apartment, of the heavenly sanctuary. The specific purpose of that ministry is to prepare a people for the second coming of Jesus.
Daniel understood there is a heavenly sanctuary--all the Israelites who were true to God understood it; it is natural then that when the angel in Daniel 8:14 answered the question "how long ...?" by saying "unto two thousand and three hundred days; then shall the sanctuary be cleansed," it's natural that Daniel understood it was the heavenly sanctuary.
That great Day of Atonement ministry is the most important activity going on today in the heavenly universe. Keep in tune with it.