If we agree that videogames are a form of art, then, IMO, from an artistic standpoint, videogame designers should be against making overly hard games.  Think about the time and creativity (not to mention, money) it took to create parts of their videogame that a large percentage of people will never get to see because of a ridiculously high difficulty.  This doesn't have to just apply to modern games.  Take an old-school "classic" such as Ghosts and Goblins.  Think about how few people actually saw anywhere past the first few levels.  People spent time creating the monsters, designing the scenery, laying out the levels, placing the pickups, etc. and hardly anybody got to see it.  It's like painting a picture and then hanging it in the closet of the art gallery.

This is one of the reasons why, IMO, ALL games should have variable difficulty settings.  There are people who relish the challenge and then there are people who are just there to enjoy the experience and go along for the ride.  Few things in life irritate me more than a game I enjoy, but have no hope in hell of beating.  Decades later, I've still never beaten Mario 3 or Mike Tyson's Punchout to name a few.

you should be able to beat super mario 3, i found it easy since its so easy to get lives.

today's games are very easy, if it gets any easier there wont be anything left, most games have difficulty settings or should by now.

Yes because art has always been populist... Some of the best art was hated in its time because it was challenging. If games are art then some will be hard, some wont, some will be great and some will be crap.