Since the 80's all of the Robin's except for Damian have been depicted as being teenagers. Damian is something of a special case since he'd probably be more dangerous if he were not out there as Robin so that Batman can keep an eye on him.
Actually, if I remember correctly, Tim Drake was 9 when he was introduced.
This is really interesting. Are all sidekicks outdated now? What really is the purpose of the sidekick?
An interesting question, especially given your avatar, as
Marvel is introducing a sidekick for Spider-Man, named "Alpha."
Which is interesting, since Marvel, aside from Bucky (who technically predates Marvel Comics, having first appeared when Marvel was Timely), Marvel has really avoided sidekicks. Yes, you can make arguments about Cap having others serve as Bucky, Rick Jones, and I guess, you could argue, The Falcon to a degree, to name a few, but while DC had enough sidekicks to form their own team, Marvel's were few and far between.
Some sidekicks give us entre into the world of the hero. Watson was not only a normal guy with whom the reader could identify, he was the narrator and chronicler of Holmes's adventures. Robin, and the spate of young sidekicks at the time (Speedy, Bucky, Butch, Boy, Jimmy Olson, and later Aqualad, Kid Flash, Wonder Girl) also were intended to give the young comic reader someone to relate to in these stories - to feel that they were in on the adventure. And, despite the bullets flying and wartime context, the tone was generally light (indeed, the advent of Robin lightened up the tone of Batman considerably, his origin notwithstanding) and the danger a fanciful abstraction.
It seems Alpha will serve in the role of giving younger kids an entre. Personally, I think Marvel realized there's only so much you can do to keep Peter young, and decided to, instead, give him a kid sidekick.
They are also trying to tie it into Peter's history with Ben serving as his mentor. With Dick, at least, the Batman/Robin relationship also served as a connection to Bruce's past and for him to be there for someone who's going through what he went through. This was added onto Tim's story, as his mother and later father died after he became Robin.
Sidekicks also served the function of providing contrast for the hero's extraordinary skills. Holmes famously remarked to Watson, "It may be that you are not yourself luminous, but you are a conductor of light. Some people without possessing genius have a remarkable power of stimulating it...When I said that you stimulated me I meant, to be frank, that in noting your fallacies I was occasionally guided towards the truth."
Which is something I always found weird about the 60's
Batman series in that Batman, seemingly to help train him, always deferred to Robin on the detective stuff, like the Riddler's riddles. It happened so much, after a while, I kind of wondered if Batman even got the clues or if he just let Robin do the hard work and then reply with an, "Exactly, Robin" to make it seem like he had already reached the same conclusion!
Sidekicks are always inferior to the hero -- either they are a comic figure like Doiby Dickles or Cisco Kid's Pancho, a youth like Robin, a racial minority like Kato or Tonto - basically someone who, even when competent, could in no way compete with the hero for the limelight. Of course, the advent of racial justice and the rise of the anti-hero did a lot to change that dynamic.
Which is why, usually through the
Teen Titans series, DC dealt with the sidekicks growing older by having them feel they needed to prove themselves. Some, like Dick, felt it best to strike out on their own, with a new identity and a hope to separate themselves from their sidekick identity. DC had others, like Wally West, develop problems and have to pretty much give up being a sidekick. Though Wally fits into another category (which Dick recently filled, himself), as the "heir apparent."
That being said, I think you are missing a key role of the sidekick, which is represented by the images the OP posted: drama. In Robin's case, it's easy to put him in the role of victim and having the hero have to deal with the fall-out of that.
In Speedy's case, it meant Green Arrow had to face the realities of drug abuse, as his sidekick was revealed to be a heroin addict. Therefore, the writers were able to tell a story about drug addiction that really affected the hero, without having to "sacrifice" the hero and have them be the addict.
So, between the "darkening" of comics and the erosion of the classic worship of the hero, are all sidekicks outdated at this point?
It seems the answer to your question is both a "yes" and a "no.
With the New-52, DC has become more "Marvel-like" in terms of sidekicks. Aside from the Robins, we really don't see sidekicks. None of the current
Teen Titans, putting aside Tim Drake for a minute, are sidekicks or protegees. As far as Tim is concerned, I guess he did work with Batman for a while, but DC recently said he was always "Red Robin" and never just, plain "Robin." Make of that what you will.
Marvel now, seems to be trying out the sidekick thing, so we'll see how that goes.
Personally, while I like the idea of a sidekick and I think a lot of good stories can be told with them, they are perhaps outdated. Putting aside the fact that they were originally an entre for kids into the super-hero comicbook world, they were also a product of a more "episodic" time. Back in the Golden and Silver Ages, the characters seemed to stay the same age and maintain a status quo.
Then in the 70's and especially the 80's it seemed that the stories became more episodic. Wikipedia puts it around '69 when they decided to write Robin out of the Batman titles by having him attend college. By the time
The New Teen Titans rolled around, we began to see the original DC sidekicks as being in their late teens/early 20's. By the mid-late 80's, Dick was Nightwing, Wally was the Flash, Speedy was a father, Donna was Troia, etc.
We'll see how Marvel handles this, but compressed time or not, eventually they're going to have to figure out if Alpha is going to graduate high school or stay his current age, which is when things get sticky (no Spider-related pun intended!).