My experience in CA and IA is that it depends on the vehicle. I've been cited for no front plate in both states. Usually it's state cops that ticket for it.
IA I had troopers turn around on a two lane twice in a year and cite me in my BRZ, along with citing for window tint. My wife's Wrangler has been going for two years with no front plate and hasn't been pulled over. In CA I went for years without being cited but eventually got nailed along with covered license plate and window tint.
CA, not a big deal, it was a $15 fix-it ticket. IA is not a fix-it, it's an actual fine.
Since the Durango is an attention-grabbing vehicle, I decided to just bite the bullet and put the front plate on, along with forgoing window tint. In CA with the fix-it tickets and cop friends it wasn't a big deal, I'd just get them signed off. Iowa was getting expensive.