Fanaelialae
Legend
If that's the direction that you want to explore in your world building then go for it!That does make complete sense, and I can see how that would act as a hard limiter on magic in the world, particularly wizards (requiring both innate ability AND wealth). And depending on how rare you decide to make that spark, I feel like this question kind of answers itself: if magic is mostly hereditary, then yeah, it's probably a common element among the ruling class and therefore your world leaders are almost certainly going to be casters. On the other hand, if that "spark" is so rare as to be extremely uncommon, then there might not be enough magic users to really consider them a social class, and it would be hard to maintain generational power if family lines can't reliably inherit the ability.
To me, magic is so variable between the classes in terms of the source that the individual is drawing from that it makes more sense that some types of magic are accessible to the average person and others aren't. Clerics and paladins gain their magic from their belief -- and sure, for many, that belief will never translate into functional magic -- but why shouldn't someone with intense belief in their god be able to pray and meditate long enough to tap into a couple cantrips and a low-level spell?
There are other kinds of magic that explicitly come from one's birth -- sorcerers, of course, but also certain races such as genasi have their own innate spells. I prefer to draw a contrast between those innate kinds of magic and ones that come from other sources.
That's a good point, it makes sense that NPCs simply don't work the way that PCs do. I'm really just using the classes as a basis point in this discussion since that's sort of the agreed-upon canon that we can look to.
That said, there are any number of reasons why someone with strong faith might not be granted clerical magic.
Maybe the gods want to limit how their power is used. Tim the farmer might be very faithful to the goddess of agriculture. However, does the goddess want to risk granting him the power to smite his neighbor in a fit of anger? She might only entrust her power to those she believes will use it responsibly. Faith =/= responsibility.
Maybe the gods have a limit on the power they can grant. Sure, the agricultural goddess could grant every farmer in the world the ability to cast create water, but that would leave her vulnerable to the god of corruption (who has chosen to be far greedier with his power).
Maybe there's a balance to the multiverse that an excess of magic could disrupt. A thousand active clerics casting Create Water on occasion doesn't significantly harm the cosmic balance. However, a million farmers casting Create Water every day would draw too much of the Elemental Plane of Water into the Prime Material, resulting in a catastrophic imbalance that would reverberate across the planes.
And, of course, maybe there's an inherent quality to some individuals that make them more receptive to divine power than others, not unlike how some people naturally have excellent vision while others may have very poor sight (or even suffer blindness). John the Cleric might have been able to tap into the goddess's power after only a few years of training. Whereas Tim the Farmer, despite having just as strong a faith as John, would have to train at the temple for several decades before he could do the same.
Even for sorcerers, just because you have power in your blood doesn't mean you have a meaningful amount. Maybe your sorcerous heritage gives you just enough magic to spray a harmless shower of sparks from your fingertips, and that's the extent of what magic you'll ever accomplish.