They are easy now because they want the games to appeal to as many people as possible. Also like many have already mentioned, they used to get stuck and move to another game. How do you expect to sell someone a sequel if they don't even bother finishing the first or it left a bad taste in their mouth. They want you to finish the game, they want you to be hooked on the story, and crave more.
I love the accomplishment of a hard game or even the hard to get achievements. I too complain that games are too easy. However, that is why I stick to the multiplayer where I will often run into players on my level or better to keep it interesting.
Just recently I was playing through all the Infamous games again after getting the plat in Second Son. I took notice along the way that in every mission, even the short 2 minute missions had checkpoints after every minor step. Whenever I died I didn't even have to repeat the mission, just put me right back where I died pretty much every time, and all I had to do was kill the last wave or whatever with full health and energy. Stuff like that I hate honestly.
Don't hold my hand through the game, they might as well just have an auto-play feature and let me watch it if its going to be that easy. Games already have easy or even very easy modes, why do they have to make the game itself geared towards casuals? You already kill enemies in 2 hits while taking 100 before you die on easy, what needs to be easier?