Because someone demanded it! A racial class for humans built on Old-School Essentials rules. Also compatible with other B/X rulesets.
Most OSR games derived from Basic roots use a race-as-class paradigm; this frustrates those who want to play dwarf magic-users and elf thieves, usually prompting a “why aren’t humans a race-as-class?” argument from those hooligans. This mini-supplement replaces the fighter, thief, cleric, and magic-user with a human racial class. Now no one gets to be a magic-user or thief: Problem solved.