I agree that they're called for due to stretching the game to a greater number of levels. I don't agree that stretching the game over more levels is a problem. It is just one possible design choice. Your later statement that, "There's no real need for the system to be more than ten levels...," seems to me to likely be specific to your own preferred playstyle, rather than a solid generalization.
Nope, it's about the math. (Aren't you the guy who regularly mods people not to attribute motivations to posts?

) It's not about playstyle, since I enjoy many different playstyles and types of games. I play many different games every year, and have for many years (37+), but you know this so it makes your discounting my point based on "playstyle" rather confounding. Perhaps you went that route because you didn't understand the implicit "There's no real need for the system
based on the d20 to be more than ten levels...," Nope, not a playstyle thing, it's about the math.
The intrinsic problems to the current d20 system stem from it being set up as a ten-level system that was then elongated despite the original math being based on a core mechanic with a range of one to twenty. What followed as the system evolved was a myriad of redesign to shore up what gets weakened by stretching the system to 20 then 30 levels and beyond. Many of the discussions being had on the game/design blogs are about the problems that have arisen from this stretching but rather than address the root of the problem they discuss ways to patch it over, or even to obscure it by making the math less apparent to the players. The scaling of skills vs. challenge ratings, and to break them down by narrative tiers, is a good example of the later. This discussion of ability score increases is part and parcel of the overall problem.
The action of leveling up is something that may players like - it is viewed as many as a perk. If you want a campaign that runs for (real-world) years of frequent play, if you have a small number of levels, then your players don't get that pleasure very often.
Now, of course, that design choice means the game is not as good for other things. For example, it doesn't work so well for representing a meteoric rise to power over short times, as what was earlier a pleasure can become too commonplace to be entertaining.
This only goes to show that no one design can be all things to all people.
All of the same can be done without leveling as often, if the perks and features are not as tied to levels.
Anyway, I'm playing in a Star Wars game right now, which also has the intrinsic stat-raises with level. I find I'm looking forward to them as an additional way to represent the character's learning and development.
I see. You're looking forward to leveling because of what is tied to leveling. That's part of my point and I'm glad you bring it up. Now imagine if all of the "perks" as you call them were untied from leveling (not saying that's the way to go, just presenting the extreme for illustrative purposes). What if ability scores, skills, class features, etc., none of it was tied to level, essentially rendering leveling meaningless. These "perks" are just floating out there while we look into the core portion of the game and we'll get back to them at some future time. For now, just leave them aside. I'd imagine at this point that most gamers wouldn't care if that game was thirty levels or twenty or ten. So, if we take away this system dependence on leveling, just for the sake of argument, and look at the best mathematical way to set up the game based on a d20 core mechanic, what truths do you feel exist? And, to ensure this is still tied to the thread's original discussion, let's take that conjecture a step further and discuss how those truths relate to a system that also wants to include ability scores (and in ranges commensurate with the versions of the system under discussion)?