That's the logical point of view, but this then leads to another question which the DFRPG books doesn't cover too much, eg how common are supernatural entities (and their actions)? If you have one wizard and a few vampires/other supernatural beings in a city full of millions of mundanes, no one will notice them, but make that a party of PCs with considerable powers and 20+ supernatural NPCs, it's a different story.
Minor talents are not THAT rare (the Paranet seems to find them in decent numbers... still a very small minority of the population though), but their talents tend not to be very visible/'flashy'. Even somebody like Mort (who's high up on the "below Council level" scale) wouldn't necessarily be obviously 'real' to a non-clued-in person (especially since he was a charlatan for a while). Mort's not flinging fire and force around like Harry. Some are fairly flashy, though, such as the Alphas.
People of faith other than KotC (eg Forthill), changelings who haven't developed obvious Faerie physical features, pre-first-feeding White Court, non-tattooed Red Court Infected, etc. will be indistinguishable from normal people, at least until they display unusual powers.
White-Council-level wizards are about one in a million, Harry (and Molly later) seem to be the only ones permanently based in the Chicago area.
Vampires we don't really know. Judging from Changes the Red Court was probably somewhat more numerous than the WHite Council, likely in the tens of thousands, but
Black Court, they're supposed to be nearly wiped out but Drulinda (from "It's My Birthday Too") was able to find one when she went looking for vampires. I'd guesstimate as rare as wizards or more so... given how powerful they are said to be compared to the other vampire courts, even a few thousand would make them a more significant power than they seem to be in supernatural politics.
White Court, nobody knows, some people on these forums say there are tons and some say probably less than a thousand. I tend to think the latter.
Ghouls seem to be around in the mortal world, available enough for various villains to use them as thugs, but not massively common.
The Little Folk are everywhere but mostly invisible to normals, I think. Other Fae are mostly off in Faerie.
Other supernaturals are also mostly off in the Nevernever.