You're of course taking the individual out of the context of the party. If you have a wizard in the party, his ability to craft (and accumulate spells to use in the crafting) benefits the entire party, just like the fighter's hit points benefit the wizard.
Thank you for that AWESOME analysis. It'll change my spell acquisition methodology. I have to admit, I was a scroll gatherer out of habit. This is beautiful. Where's my Blessed Books?!