Yes, absolutely correct that sufficient shelter must be provided, if you kept a frog in a bare box it would no doubt be similar to putting a human in the middle of the desert with the resulting over-exposure. Animals self-regulate in the same way that we do, but of course must be given the opportunity to do so.
I take on board what you're saying about people who just want a 'pet', I think the issue I have is when (as I have seen on here many times) new keepers are told that this very basic way of keeping animals is the correct way. I believe everyone should be encouraged to keep animals to the absolute best of their abilities and we are very fortunate these days to have the equipment and the knowledge to be able to do so, it's the responsibility of the more experienced to guide the novice in the best direction (I feel). This does include larger enclosures than the 'norm' for sure, many recommended sizes have no hope of providing proper photo and temperature gradients let alone enough space for the animal.
As far as the Horned Frog is concerned, I've never kept them so I can't argue against what you have heard from people who breed them (I put this in the Tree Frog section as it's my area of interest), but it's worth noting that in the snake side of the hobby, big breeders like Brian Barczyk have an enormous following and the keeping methods he recommends (keeping large constrictors in bare tiny tubs and drawers) are emulated by thousands but also abhorred by just as many people so opinions do vary!
Papers like the attached along with easily accessible information on for instance the Arcadia website are thankfully becoming more common and are a resource to help people know how to provide UVB for their animals without the need for an expensive meter. For me (and I remember all the shortcomings of the pre-UVB era only too well) it's something to point people in the direction of as they strive to care for their charges in vastly improved manner from 'the old days'. Also, we shouldn't forget that benefits of simulating natural sunlight are not just limited to the d3 production, even most people who argue the synthetic oral method will grudgingly admit this.