The adventurer business is a sustainable business. And although Sharlayan has the best schools, the Eorzean schools are also excellent.

After hundreds of thousands of children were orphaned by the Calamity, the Eorzean Alliance invested large sums of money to found boarding schools throughout the Realm. Since then, every child has the right to study poetics (including languages), mathematics, mnemonics, philosophy, law, lore, esotericism, etc..., and also learn the basics of combat in the Hall of Novice (which is also part of the program, for those who wish to pursue a career as adventurers).

The subjects are provided to the Realm's schools by Rowena's House of Splendors, as soon as their paid researchers decipher and unravel the knowledge of the allagan tomestones that adventurers are able to unearth.

In this way, young people study the same subjects that the ancient allagan studied/created in the past. And that's why our WoL (perhaps one of those orphans) has so much knowledge in operating allagan machines.

He/she (and other adventurers) is now supplying allagan tomestones to Rowena, so that new children can become adventurers in the future (and acquire some equipment in the process).