With regards to the importance of non-human races as player characters, they are not important to me, but having them- especially the Tolkein races and gnomes- as an option is (to me) part of D&D. Then again, parties with non-human PCs (especially, multiple non-human PCs) has never been a big part of the D&D experience for me. Excluding both a game using the Dragonlance module and my, briefly run, half-elf character, at best, I have encountered exactly 10 non-human PCs in my first 30 years of D&D gaming (including our experiments with D&D fantasy using Hero, GURPS, and Rolemaster). This is both as a player and DM. Also, I have never encountered more than 1 non-human PC in a game at at time (again, excluding the Dragonlance game which lasted only a few sessions).
The first non-human PC I encountered was a half-elf magic-user/thief played by a friend in 1980. I didn't see another non-human PC until 1983 and 1984 when my brother played a half-ogre fighter and a friend played a gnome illusionist who spoke like Yoda (they were in separate campaigns run by me).
In 1985, I also was in a game with one dwarf, a half-elf, and a kender as pcs while at university However, the DM was running the first Dragonlance module with the pre-gen characters. Following that game, it would be another seven years or so, before I saw another nonhuman PC. The first was a gnome necromancer in 1992 or 1993 followed by a dwarf fighter a year or two later (both were campaigns run by myself).
Finally, between the late 90's and 2007*, I had seen 1 lizardman (Barbarian), 1 dwarf (fighter), 1 halfling (Barbarian), 1 half-elf (sorcerer), and 1 elf (rogue) as PCs and and each was in a separate campaign (the lizardman, dwarf, and elf were in campaigns run by me).
* After 2007, my gaming has focused, primarily, on superhero rpgs with some sessions of modern Men In Black/ Freaky LInks/Special Unit 2 inspired gaming using Savage Worlds, and experimentation with a few other non-fantasy game systems.