ELI5 Screws - why do we have two different types?

Why do we have two different types of screws?  If the Phillips head is superior, why haven’t flathead screws just been phased out over time? What are the benefits of the Allen and Torx type screws? Why do manufacturers like IKEA like to use Allen wrench screws for self assembled furniture instead of standard Phillips or flathead screws? ... we explain like I'm five Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion: darthhfaded, dmullaney, lucythefur, nagmay,dusktheumbreon and hawkeye18 To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected]