Chucklas is right, it all comes down to what you're willing to accept from a game. Obviously not near enough people can handle game dead ends anymore and to me that's a shame, but I can live with it. But the player should be enforced upon to be as observant as possible and act responsibly in the game world. It's not free easy ride. If you miss something in real life you miss it. That's that. At least in adventure games you get saves!
And yes, players should totally be punished for not being observant in an adventure game. That's half the gameplay. No, that
IS the gameplay. Even puzzle designs are all about being observant and figuring things out with some logical reasoning.
Take KQ5, your goal from the beginning is to make a trek through the mountains to the other side which is cold and perilous and also represents the next stage of the game and your journey. Common sense states that once you go that way eventually you won't be coming back (or at least, it should, especially considering how much work you have to do before getting past that snake), so you should double-check everything because it's a large game world and there must be SOMETHING you might have missed. And if you're observant enough you'll find it and move on, or at least make a save and come back later if need be. Now, if the game punishes you for not taking in the game world and exploring everything possible then I say it's not lazy programming, it's justifiable. I rather put the blame on myself the player for being too lazy to explore as much of the game as possible.
The whole point of adventure games is adventuring into a whole new world. Adventure. ADVENTURE! Why
wouldn't you go exploring everything you could and taking in the game atmosphere! And if you don't then shame on you! You're missing out! You should absolutely be punished because, in the words of an amusing internet meme, you're not doing it right. Games that don't have many hotspots, give you all the items you need at all times, offer you hints for everything without letting you find them yourself (ie- thom's point of putting hints in the many interactions themselves), creating a safe pathway that's impossible to fail or go astray from, etc is lazy
adventure game design. I should be rewarded for checking out as much of the world as possible and punished for not doing so. I don't want a quick an mildly amusing little stroll through BTTF, I want an
adventure through the fantasy world of King's Quest that will wow me at every turn and reward my attempts to further my own gameplay by making it necessary.
That's me, anyway.