Should there be negative Racial Adjustments to ability scores in DnD? If an entire race in a fantasy setting is between 2 and 3 feet tall -- why wouldn't they get a negative modifier to Strength? Ok, let's define some terms before we answer that because DnD is AWFUL at defining terms. Stats are not one thing. In keeping with other game concepts that are amalgams like HP (luck-health) and AC (defense-resilience) -- any of the core stats is also an artificial cluster of traits that makes up the nature of a character. Here is the quote from the PHB: "An ability score is not just a measure of innate capabilities, but also encompasses a creature’s Training and competence in activities related to that ability." So, when it comes to Strength, the designers of DnD have clustered three very separate ideas -- power, athleticism, and training. While size (being 2ft tall) correlates to having low power it also correlates to having high athleticism as athleticism is aided by having a high strength to weight ratio and size, whereas size has no correlation to training. We cannot differentiate whether a character is strong, well-trained, or athletic by a high strength score -- as the measure is for all three, but we may argue that access to the very top levels of strength should be reserved for characters in the upper echelon of all three. Let's try to glean something from how you use Strength in the game. The stat strength gives us a bonus to damage with some melee weapons, and it drives one skill -- athletics, which is used for jumping, wrestling, and climbing. Dexterity can be substituted for Strength for many light melee weapons, making it Strength modifies a d20 with up to a plus bonus, or as low as a minus five penalty -- which equates to a 25% swing in each direction. This means that a contest between the strongest, most well-trained, character and the weakest, least trained character is going to result in a loss for the strongest, most athletic character 14% of the time. In this world Stephen Hawking would have a 14% chance of besting Thor Bjornson in a lifting/ pushing contest -- and that is if you gave Stephen Hawking a strength score of 1. Why is that intellectual diversion necessary? We need to understand not only what the Strength score means as defined by the rules, but how it PLAYS as defined by the rules so that we can judge what kind of world is created when we fiddle with the scores. An adjustment to a stat, any stat, up or down by two points results in a plus one linear shift along that probability slide. Having a low score is not catastrophic. Having a low score in a core trait, however, is absolutely sub-optimal. Because DnD ties all class abilities through these amalgam measurements, this artificial group of unrelated concepts, a player who brings a character to the table against a "correctly-constructed" character is at an immediate and irrevocable disadvantage for their entire career. Because DnD builds so much from the concept of ability scores, tying ability scores to race reduces choice in the game. DnD is already stupid and non-sensical when it comes to ability scores, why the hell would you introduce "logic" to make it less fun? So yes, it doesn't make sense that a halfling is good at pushing a Half-orc. But, seeing as the numbers are stupid any way that you look at it -- that the whole rolling mechanic leads to stupid results from the get-go -- the damage done to the game by the negative ability score adjustment is less than the damage caused to the diversity of the game by the lack of choice when it comes to race-class combinations.
We have to make the decision based on what DnD 5e is, not what some fanboy or fangirl want it to be. I agree that negative ability modifiers for races make sense. They would be logical. But, we should never apply that logic to playable races. Logic has to be constrained by context. If that context is that an ability score is a pastiche of concepts that has a dubious relationship to the outcome of any check, and that that amalgam drives the class options and abilities, then perhaps we shouldn't think that being logical about one aspect of a lopsided conceptualization is good for anything. If the race is playable -- no negative adjustments. If you let the player play a golden retriever puppy, fine. Give the puppy a penalty to intelligence? No.