Neonchameleon
Legend
But that's not the narrative role of halfling PCs. The game has four or five players to every DM. And as a PC race halflings have synergistic thematic roles. If DMs and setting designers are too lazy to think of anything interesting to do them that reflects badly on the setting designers and DMs - but is almost entirely irrelevant to the PHB.
"Two very powerful and deeply rooted themes". That are almost literal opposites. There's the tree hugging Dr Doolittle playing Forest Gnomes and the technocratic underground dwelling Rock Gnomes. And these two themes are strongly in conflict with each other without the conflict playing out in the race dynamic at all. Such an unresolved dichotomy just makes them more of a mess than if you were to wipe one or other tradition off the map or separate them into entirely distinct races.
Meanwhile, ironically, both would be thematically stronger as subsets of halflings. No one plays forest gnomes because halflings make the better woodsmen, being stealthy and dextrous. And halflings have a natural affinity for stealth and forests. They are what happens when bigger folk push halflings right to the edge where they have to scrabble for survival (except halflings are better at it than gnomes). Almost no one likes forest gnomes because they are lightfoot halfling wannabes whose big thing is playing Dr. Doolittle when the lightfoot halflings are actively stealthy and nimble - which is precisely what you'd want for forest tricksters. And if most of their personality traits are identical to halflings that makes them even more redundant.
Meanwhile rock gnomes are at least something. They are almost opposites to forest gnomes in some ways, but they'd also make a great halfling subrace if we want subraces. Thematically they fit - the race that is interested in comfort is also interested in making things to save themselves effort and to make themselves more comfortable. +1 Int (which they'd get as their subrace bonus) is 90% as good as +2 for a class in my experience (if using the Standard Array then +1 will get you to 16) - and +2 dex is also obviously thematically good for a nimble fingered artificer (while +1 Con is not). But having a race where everyone is a tinker is mostly useful for bad comedy (and I forget who said that the worst thing about Spelljammer is that it let Tinker Gnomes off Krynn). The thing is that gnomes offer no other baseline because the rock gnomes are so distinct from the halfling wannabes. Meanwhile if rock gnomes were a subrace of halflings they'd have 100% of the PC potential of rock gnomes. But at the same time they wouldn't be an extremely silly race taken as a whole (which is a win) and would encourage DMs to make more use of halflings and make them a bit more nuanced (which is a second win)
You're only talking about rock gnomes there. Even you seem to have forgotten that forest gnomes exist. Halflings are more popular as rangers ffs - and that should be the forest gnome's thematic favoured class. But it isn't because halflings make better forest gnomes than forest gnomes.
If even you seem to forget forest gnomes at all in your defence I think we can consider forest gnomes a failure.
Things called gnomes appear a lot in fantasy literature. Taking two of the most popular fantasy series of all time, the Harry Potter gnomes are about a foot tall and garden pests used only for comedy while the Discworld gnomes are about six inches tall, ride birds, and can get very violent. What do these have to do with D&D gnomes other than the name. The word "gnome" is thematically incoherent both in D&D and outside it.
On the other hand the word "halfling" is not a name any race would give itself - but at least it tells you something about what it actually refers to. Which is another reason I think that gnomes would do better folded into halflings; "halfling" tells you which of the 58 different versions of gnomes they are while "gnome" could easily be something a race would call itself.
