This is the answer to your question: "Why?"
Ephesians4:11-15
11And he gave some, apostles; and some, prophets; and some, evangelists; and some, pastors and teachers;
12For the perfecting of the saints, for the work of the ministry, for the edifying of the body of Christ:
13Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ:
14That we henceforth be no more children, tossed to and fro, and carried about with every wind of doctrine, by the sleight of men, and cunning craftiness, whereby they lie in wait to deceive; 15But speaking the truth in love, may grow up into him in all things, which is the head,
even Christ:
Matt:15:
7Ye hypocrites, well did Esaias prophesy of you, saying,
8This people draweth nigh unto me with their mouth, and honoureth me with
their lips; but their heart is far from me.
9But in vain they do worship me, teaching for doctrines the commandments of men.
2 Thess. 2: 10 And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved.11 And for this cause God shall send them strong delusion, that they should believe a lie: 12 That they all might be damned who believed not the truth, but had pleasure in unrighteousness.
Ephesian 4:4 There is one body and one Spirit, just as you were called to one hope when you were called; 5 one Lord, one faith, one baptism; 6 one God and Father of all, who is over all and through all and in all. (This is the reason I tell anyone who will listen:
Philippians 2:12
Wherefore, my beloved, as ye have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling. 13 For it is God which worketh in you both to will and to do of his good pleasure.