Cap'n Kobold
Hero
"PCs are special" is one of the tenets of Eberron, and casters are no exception. Most people can learn to cast a spell eventually, but often only one or two, and as rituals. Actually having spells slots that renew every day and can cast different spells from is very much a PC, and a few others with the "spark", thing.I like to think of arcane magic as requiring a spark, without it you can't learn magic at all. This goes for all the arcane classes: wizard, bard, sorcerer, and any subclasses that are based on them. The exception is warlock, anyone can become a warlock because the entity you make your deal with will graft that arcane spark directly on your soul.
In practice, this doesn't really come up, it's more my headcanon as the editions have evolved.