WWE has Brock Lesnar for an extremely limited amount of time. What we know about his contract is that he's booked for a match at WrestleMania and SummerSlam, and has limited appearances between those two events. There's a chance he doesn't even show up between SummerSlam and the Road to WrestleMania, simply because he doesn't have to! Knowing that Lesnar only has three, possibly four matches in him before he fades into obscurity, what would you do?
A) Book him against a mid-card or upper-mid-card talent that needs a huge push. This could have gone to somebody like Dolph Ziggler, Kofi Kingston, Zack Ryder, etc etc. But two things definitely come out of this situation: 1) they're going to lose the match, and it's going to look painful, and 2) Brock isn't going to be happy about facing ANYBODY put a top star.
B) Book him against your top draws and milk as much $$ out of his limited appearances as humanly possible. John Cena handled the first match, beating out Brock in an Extreme Rules match I'm glad to say I was in the audience for. So who's left? He's going to face a legend or Hall of Famer at WrestleMania. Probably the Rock, maybe Steve Austin, a long-shot the Undertaker. SO with one or two spots open to face Brock Lesnar, you've got Sheamus, Randy Orton, Triple H, CM Punk and (Maybe) Chris Jericho as your top faces that could get the job done.
The money match is Triple H, and it's as easy as that. The OP may have no interest in seeing Brock Lesnar vs Triple H, but there are a LOT of fans who are dying to see it happen. I personally don't want to see CM Punk take that kind of fall right now, and the idea of Sheamus or Jericho bores me to death. And Randy Orton? Not sure that management is super high on him right about now...
But this thread wasn't completely about Brock Lesnar/HHH, even though it devolved into that. It's about why Triple H keeps coming back and "sticking his big nose in everything". Well, the simplest answer is that he's a professional wrestler. Yes, he's a part of management and a big cog in the machine backstage, but he's also one of the best damn in-ring talents and promo guys pro wrestling has ever seen. He's also still a good draw for both TV ratings and PPV buys, and instantly legitimizes most of the segments he's inserted into.
Vs. Brock Lesnar: Lesnar and Heyman are filing suit against the WWE, and have been causing a general amount of chaos. Is it not the new COO's job to come out, as a boss AND as a wrestler, and straighten things out? I'm not getting into this too much (see: above), but it does make sense from a storyline perspective.
Vs. The Undertaker: HHH returned to face the Undertaker at WrestleMania. This was booked, not surprisingly, as the Deadman calling out the now-business executive and COO Triple H, rather than the previous year's flipped situation. Not only was the build-up to this one of the best things about Raw every single week, but their match was incredible and told one hell of a story. Go ahead and complain that he was taking time away from the young guys on the card, you're an idiot. Probably.
Vs. CM Punk: Why did HHH return to "mess up" Punk's hot streak? In storyline, Punk had taken the WWE Championship, left the company, and in the process had Vince McMahon relieved of his on-screen duties. Triple H, the actual behind-the-scenes guy taking over for VKM, was appointed his successor, which makes perfect sense. Triple H actually put over Punk by giving him a title match against Cena, refereeing the match, and counting his pinfall however invalid it may have been. And then yes, Triple H beat Punk in a match at a PPV, but his job was on the line! Plus, how many people interfered in that match? That match wasn't SUPPOSED to be Triple H "burying" Punk, it was supposed to be them setting up a Punk/Nash match, which simply never happened because of injury and schedule conflicts (thank god). Do you want to know what ruined Punk's run? It wasn't Triple H, it was whoever decided that Alberto del Rio needed to be added to the mix, flip-flopping the title between Punk, ADR and Cena for several months. That's what killed it... Plus, if you'll notice, PUnk isn't dead. He's been WWE Champion since Novemeber, so quit your bitching.
Before this he returned to face the Undertaker for the first (technically second) time, and before that he PUT SHEAMUS OVER and remained out for the better part of a year. Now, somebody please tell me how Triple H has ruined everything ever, and is the root of all of WWE's problems in 2012. I'm begging you.