Obviously Hepler Mode doesn't make sense in all games. Add Hepler Mode to Super Mario Galaxy and the game would just be a long sequence of incongruous scenes of wooshing stars. You couldn't add it to Skyrim, since the combat and looting and story and puzzle elements are all mixed together, so there isn't a clear delineation between "combat sequence" and "story sequence". If you added it to Asteroids then the game would simply cease to exist. If you added Hepler Mode to Torchlight then ... I dunno, what would that look like? Just selling a pool of infinitely-replenishing vendor trash, forever? Whatever. The point is, it wouldn't make any damn sense.
But in a story-driven game with dialog trees, skipping the combat can make a lot of sense. I was really into The Witcher 2. I liked the situations and I was interested in the lore. I loved how it moved away from the BioWare Paragon Doormat / Renegade Jerkface based decision making and just presented messy situations and let you deal with them as you saw fit. I wanted to know where the story was going, but the combat in that game was a dull chore. If I could have replaced the combat with vacuuming or washing dishes, I would have stood a better chance at making it through the game. Instead, I shelved it. I'd totally be willing to take another run at the game if I could skip the fighting and just explore the world and the lore. (Yes, you can watch it on YouTube. But if you do that you can't explore, make decisions, or control the dialog.)
The Trayus Academy sequence in KOTOR 2 was painfully long, repetitive, and boring. If I could have pressed a button and skipped right to the end of that section, I would have done it in a heartbeat. Same goes for large sections of Neverwinter Nights 2, when it felt like the combat was needlessly padded and the game was just blatantly wasting my time.
"Games are about gameplay!" screams the crazed purist. Actually, games are about fun, but even if we accept the premise that we're here for gameplay it's worth pointing out that dialog trees are gameplay too. A properly constructed dialog wheel should let you make decisions about how things play out in the world, let you use your dialog-based skills to get your way, and uncover new lore. Why is one type of gameplay skip-able and not the other?
If anything, the fact that Hepler Mode is possible is an indictment of the cutscene / combat / cutscene / combat / cutscene style of game design. I much prefer games where the story and combat are blended organically, so that you don't have to stop doing one so you can start doing the other.
Maybe instead of adding Hepler Mode, developers should make games where the story and gameplay are in harmony instead of competition. But if Hepler Mode is possible - if combat is nothing more than an obstacle between cutscenes and nothing you do in a fight will have consequences later on - then I don't see any reason not to give players the option.