Why is red phosphorus used in safety matches?

Red phosphorus is used in the manufacturing of safety matches because it is nontoxic and not subject to spontaneous combustion, unlike white phosphorus.1

The invention of the safety match, patented by J.E. Lundström in 1855, relies on the separation of combustion ingredients between the match head and the striking surface. In this design, the red phosphorus is incorporated into the specially prepared striking surface rather than the match head itself. When the match is struck against this surface, the friction generates enough heat to convert a small amount of red phosphorus into white phosphorus, which then reacts with the oxidizing agents in the match head to initiate combustion. This method provides a safer alternative to earlier match types that utilized highly reactive and toxic white phosphorus.12