Out of how many characters overall?
If your sample size is 20 what you're saying is much different than if your sample size is 200.
Somewhat shocked that you saw so few Rangers, regardless.
Good point.
I'm going to give a random gut assessment of about 60-85. I started with the Mentzer Red Box, so there's a lot to have to remember. For me though, psionic classes haven't seemed to be much rarer in actual play than some of the other classes.
Except we never got an "Artificer's" handbook. We got a complete setting guide with, what, five pages detailing a class that doesn't actually use any new mechanics. There's no "spell points" or anything like that for artificers. Other than a somewhat different casting progression, an artificer introduces no new mechanics at all.
OTOH, people seem to insisting that we get a completely new class with a psion, and that it MUST NOT use existing mechanics. Because, apparently, a psionic wizard or sorcerer isn't good enough. Nor are the five or six other subclasses we've seen for psionics in the last little while. No, it must be 100% new and it must not be in any way similar to a wizard/sorcerer.
I'm thinking that that's a bit much to ask for for a class that not that many people actually want in the first place.
I'd be completely fine with a write-up in the Dark Sun book of similar complexity to artificer. I want a class, and psionics flavored as "different", and hearkening back to presentation in prior editions. You could do that without adding any systems that are more complex that current classes have. After all, the artificer added new systems. The class doesn't have to hit everyone's ideal (including mine). I'm totally on board with a lowest somewhat common denominator here, as long as it's an actual class.
For example, here's a simple bare bones way they could make a class that would be more satisfying than not making one:
Psion
d6 HD
Saves: Int, Wis
Armor: Light
Weapons: Simple
Skill: 2 from a suitable list
Psionics is described as a mystical power that some consider is another category of magic, different than arcane or divine, while others consider it to be something else entirely. For mechanical purposes it counts as magic (just like the Psionic abilities of monsters do). We'll call their "spells" powers, and the act of "spellcasting" manifesting, though they use all the normal rules except where noted.
Full spellcaster with the standard spell slots. A prominent sidebar encouraging usage of the Spell Points system on Page XX of the DMG.
They don't need any components for their spells, unless those spells normally require costly material components. Encouragement to refluff those components into other objects of the same cost but more psionically appropriate (crystals, etc) is given. They have noticeable indications when they manifest their powers. It'd take a sentence or two to describe that (let's say), verbal components are generally replaced with auditory indications, somatic components with visual indications, and material components with olfactory indications. (They could do better if they spent more than a minute thinking about it). Give about 4 examples of each, and say they can vary by power and individual psion.
Give them the high end of cantrips (or maybe one extra).
Give them a pool of points they can spend to manifest powers in higher level slots. Make the numbers work out such that it could be easily added to spell points (or convert into twice as many spell points). The points refresh on a short rest.
At high levels, give them the ability to manifest unlimited 1st (and maybe even 2nd) level powers. Perhaps levels 18 and 20.
Give them their own powers list, mostly selected from published spells. Take all of those spells in this travesty of a UA that came out and make them exclusively part of their power list--no one else gets them.
Make the 6 traditional psionic types into subclasses. Or save space and combine them into three (1st = telepathy+clairsentience, 2nd = psychokineticism+psychoportation, 3rd = psychometabolism+metacreativity; or switch psychoportation and metacreativity).
Each subclass gets some simple appropriately themed abilities every few levels.
That was just me, off the cuff, never having attempted to make a psion class before. I could come up with a better one if I took a day, or a week, or a month on it. If someone did take that month, I'd bet they could come up with something most fans of psions would like enough to use without much house ruling. Sure, some people didn't like 3.5e psionic classes, but they worked just fine and I'm sure the book sold perfectly fine. Give us something like that in the Dark Sun book and I'll be happy.