The other question Fabio had on the post about extending first level class abilities to everyone was about magic use. If anyone can cast 1st level spells they know, can a barkeep cast a Clean or Grease cantrip?
Well, maybe. But does the barkeep know those spells? Are they available for study? Can the barkeep afford the training?
What I was getting at when I stressed the idea that these are base level abilities is that anyone can try them, regardless of class, and will be as good as any other 1st level character. However, there's an assumption that the character has the appropriate tools. Non-fighters could fight without a weapon, using just their fists and feet, like any unarmed fighter, but shooting an arrow requires an arrow and a bow. Picking locks or removing traps requires lockpicks and delicate tools.
Spells are a magic-user's tools. To be able to memorize and cast a spell, you must actually know the spell, and have it in a spellbook. A magic-user gets a first-level spellbook to start out with. A Fighter, or for that matter a barkeep, could get a spellbook and learn the spells therein, under this system, but doesn't automatically have any spells at all.
It's a question of potential magic versus actual magic in play. It applies even to campaigns that don't allow anyone other than a magic-user to learn and cast spells. Sure, a magic-user can cast Fireball. But does anyone have a Fireball spell the character could buy? How much are they charging? The fact that magic exists in the game world doesn't mean it's as common as dirt.