Nintendo's certainly not the only offender but they're the worst. If you die say, five times, on any level of Mario they give you a 'Win level' button like the white tanooki suit. You can't even turn that off.
I actually like the way that Nintendo handles difficulty. The Super Guide feature (which will automatically beat a level for you) only shows up after you've died X number of times and it permanently marks your save file as having used the Super Guide. It gives you the option to cheat, but it discourages you from using the cheat. I Wanna Be The Guy did the same thing with putting a pink ribbon in your hair if you play below hard difficulty.
Yes, Nintendo games are still too easy (even Donkey Kong Country Returns), but they have a few moderately challenging parts here and there. The Super Guide is a good compromise and allows Nintendo to put some degree of difficulty in their games without worry of scaring off their casual fanbase. It's not ideal, but that's why it's a compromise.
Oh, and for those of you who think there's too much hand-holding in games today, check out this video showing what Quake would look like if it was released today. The video has more than 2 million views on YouTube, so it clearly resonates with many gamers. It's very cathartic.