Again since for 4th and later in 5th edition.org and half orc have diverged into two different archetypes.There was: adding human to orc made orcs possible to be more intelligent, adaptive, skilled, and have non evil morality. In short, able to be a player usable species. Once you make orcs capable of being as intelligent, skilled and moral as humans (or other species) the rationale for a half-orc rapidly declines.
To a certain degree, the half-elf has floundered since 3e and the lifting of restrictions on elves. The half-elf, mechanically, was a compromise of elf (the best racial trait package in the game) and human (the race with the best class options). Once elves could be any class and humans got actual features, the half-elf lost it's spot as the compromise race and awkwardly tried to be the charisma and skill race (aka the bard race) for three editions.
Both races have lost there niche of "orc, but playable" and "elf, but more class choices" they kinda drifted into "strong, race" and "talky race" and with the movement of ASI to background, have nothing unique to hang their hat on.*
* Before you jump in with the mixed heritage analogy, I will point out I'm discussing mechanical aspects, not story ones. Neither race brings anything mechanically interesting other than "has some features of two already playable races". As for the analogy, their is nothing unique about that which couldn't have been done with any half-species. We are talking about half-elves and half-orcs and not half-gnomes and half-goliaths because of tradition. I'm not saying mixed heritage species should not exist, but I'm saying the rationale for these two specific ones are flimsy. It is basically a call to tradition and not much else.
The issue is only fans both species recognized and roleplayed this