Yeah, it kind of depends on how useful your priests are. Some nations have magepriests (magic paths + holy), which probably means you'll have more of them around because they're actually useful. Some nations have priests that can do fun things like raise undead or smite really well, so you might have more of them around. Some nations have terrible priests (holy 1 or 2) and few useful sacred units (so blessing is nearly useless) so there's no real reason to have priests around.
On this topic, I actually have a question.Caelum used to be my go-to nation, partially because of the flying holy-3 stealth priests. I recently realized how utterly useless preaching is though (for the most part at least. I think the manual's wrong on the actual numbers for this, so it might be better than I think) so are they actually good for anything other than smitespam/morale boosting mammoths?