Okay, so I really don't like the idea of the half-orc "race" in gaming. Apparently the idea comes from the Uruk-hai in The Lord of the Rings and first appeared in AD&D (even though I don't remember it). I don't like idea for two reasons: my basic mental picture of orcs and the subtext of how an orc would mate with a non-orc.
First off, let's take the mental picture. I remember paintings by the Hildebrandt brothers in a Middle Earth calendar I owned way back when. One is a scene with the orcs sitting around a fire at night with Merry and Pippin tied up nearby, the other a scene from a siege. The orcs are depicted with porcine faces, rather like green pig-men or boar-men. Otherworld Miniatures in the UK has a cool-looking line of miniatures with this look. I rather liked that visual concept for them. Later I played AD&D and the drawing of them in the Monster Manual also had the piggy look. So that's how I always thought of them for gaming. The AD&D orcs were a race of boar type beast-people: ugly, smelly, aggressive, dangerous, and violent. No "normal" person (human, elf, dwarf, etc.) would consider mating with them and besides it wouldn't be genetically possible for any mating to be fertile. I quite literally never considered that such a creature as a half-orc would exist.
Secondly, there's the subtext of rape. There really is the built-in suggestion that any half-orc must be the result of a violent sexual assault by a male orc against a humanoid female. I find that disturbing because that subtext was unnecessary. If the game designers wanted to add a playable race with attributes which complement the fighter or barbarian classes (in the way that the elf complements the wizard or the halfling complements the thief), why didn't they come up with one which stands on its own? They later added the dragonborn, the warforged, and the goliath. All of those are strong/tough races which appeal to players. So why add a race which implies that all of its members are evidence of a crime? Was it to be more gritty, more edgy, more hardcore, more badass? Perhaps, but the rest of the game didn't move in that direction. It stands out as a design decision. And if the orcs aren't the evil monsters of their reputation, but rather a misunderstood proud tribal people, why not just make them a playable race directly the way World of Warcraft did? Really, I would prefer to have orcs or hobgoblins as a player race straight up than half-orcs.
There's also the question of half-orcs being accepted into humanoid society. I just don't find it credible that half-orcs would be accepted in most "civilized" areas. Sure, you can make that aspect of the character background an element of the campaign and roleplay the interactions. But wouldn't half-orcs be so rare as to be seen as freakish half-monsters? Well, perhaps you could have an area of the campaign world where invading orcs wiped out the defending human army, thus killing most of the military age males, and then proceeded to settle on the land and take the women as "wives". An entire generation of half-orcs would ensue. I vaguely recall something like that happening with the mongol invasions. Perhaps if the orcs remained for a couple generations and then withdrew, much as the mongols withdrew from their conquests in the west, an entire region might be left heavily populated with half-orcs. Several generations after that, or maybe a century or so later the "people" of that area would all be half-orcs but much removed from the original invasion. That would be a more plausible way to have significant numbers of half-orcs in a campaign world with less social stigma, at least in neighboring countries.
But for the campaign world I'm working on the orcs will be the boar-people of my early imaginings. They will be one of a number of "beast peoples" created by the nature gods of earth, sky, and sea in imitation of the First Races (dwarf, human, and elf) created by the First Gods. As literally the children of a lesser god they simply are not cut from the same cloth as the First Races. The nature gods shaped them using the animal creatures of their respective domains and have not the power to endow them with the same higher innate intellect and cultural talents of the human, elven, and dwarven civilizations. The orcs and other beast peoples are closer to nature and the nature gods. They are more feral and animal-like in their behavior and social structures. And thus they must remain, for such is the essence of their being.