Why would a company use backward vertical integrations?

A company would use backward vertical integration for a number of reasons the main reason being to protect its supplies and defend itself against a lack of good quality reasonably priced raw materials it might merge with or takeover from the company it buys its materials from the company will therefore get all the supplies it needs at cost price.this thereby helps the company to compete in the market as it can charge lower prices for its goods and therefore increase its sales(price penetration strategy)