I'm about to go to bed so I'm not going to get into a lot of detail, but basically game publishers and designers are only out to make a quick buck, and they can't do that if people are constantly getting frustrated at the complexity or difficulty of some games. To make more money they have to appeal to a wider audience, and that means making games simpler and easier to beat.
Really the game industry is just trying to keep itself afloat, and this is the best way they see how to do it; appeal to as many people who don't have the time, energy or skill to beat a half decent game as possible. Which means designers dumbing down their games by emphasizing less on the development of skill and problem solving by the player to win. This isn't the case for all game designers, but as you have noticed this is becoming more and more of a trend for quick money making.