Personally? I feel like... hmm.... how to put this.
Back in the day, you had the arcade. Now, there was a very kind of niche home-brew market for PC games back in the early parts of the 70's, but arguably you wouldn't have the videogame industry as it is now without the economic impulse of the arcade boom. Those machines made a lot of money, and the early experiments with home-based gaming was essentially an attempt to cash in on the arcade game craze.
Now, when you're making an arcade game that makes a lot money, you're trying to design a game that makes you run through quarters rapidly, and on a regular basis. And on top of that, you want the player to have fun while they're doing it. You want people to want to put their quarters into those slots, and you want people lining up for a turn to put their quarters in. A player that can last fifteen minutes on one quarter is a good player, but they're not making you as much money as five players that can only last three minutes, obviously.
So early games were designed to be pretty difficult. You wanted a bit of a difficulty curve so that it didn't start out too tough, and you wanted just enough of a challenge that players could feel like they were getting better and improving their high scores. But basically if you were a game designer at that time, you were trying to make a game with the difficulty particularly balanced so that your average player was paying in at a pretty regular rate. I'm sure some of these guys had charts and graphs worked out and an ideal "quarter to play time" ratio they were going for.
So when the home systems start coming out, not only are a lot of them ports of popular arcade games, but the majority of the games were still largely influenced by this game design paradigm. People liked playing those arcade games, so those sorts of games were going to be more popular. Look back at most of your NES or Sega Master System collection, even, and you can see that clear influence in pretty much all of their games. Limited lives, pattern recognition, difficulty ramping, when you die you start back at the very beginning of the game, etc.
But economically, what works for an arcade game isn't necessarily best for a home system (and I'm lumping PC games in with "home system" at this point - by the mid-80's you have somewhat different markets, but my basic points still apply equally I feel.)
What you really want with selling a videogame for a console or PC is you want to build brand loyalty. You're making a one-time profit off of each game sale - it no longer matters how long the player plays your game, how often they will die, etc. Ideally, you want to make a game where the player is playing that game and not someone else's. You want each game to maintain that player's interest just long enough for your next game to come out, or to leave enough of an impression that when you do release your new game that they drop everything else and spend their money on that instead of a competitor.
So, naturally, some measure of playing into your target audience's power fantasies and ego is going to go a long way, here. Do you want the game that makes you feel like you're not very good at it, or do you want to play the game that makes you feel instantly powerful? (That's rhetorical, by the way.)
... And I'm kind of going off on a tangent, and it's actually really late and I've just come off a 13-hour shift. So before I lose my thought, here: THe thing to remember is that (barring DLC and micro-transactions,) unlike an arcade game, you're only making a one-time profit off modern games. You want to make a lasting impression, and there's no innate upside to killing the player (unless that's the niche you're trying to fill of course.) So you see things like checkpoints and game saves, etc - now instead of wanting to keep the player from "beating" the game, the impetus is more along the lines of... well, you put all this effort into making all these levels and characters and plot points and wouldn't it be nice if people could actually see all the work you put into it?
In short - yeah, games have become easier in many ways, and more user friendly. But I do feel like there's some pretty compelling reasons for why things are the way they are. And I also think it's important to keep in mind that if games are becoming easier for more mass appeal (though mass appeal has always been the driving force of the industry - where would we be now if everyone didn't get Pac-Man fever after all.) Anyways... it's also important to remember that back in the day games were difficult basically just for the sake of being difficult. And to make more money off you.