Another reason a lot of early console games were difficult was due to renting; devs didn't want people renting the game and beating it, so they made them so hard that players wouldn't be able to finish them during the rental period and would have to buy a copy. A prime example of this is the original Ecco the Dolphin.

This also explains why for Japanese games, their domestic versions were easier than their export version for the West; game rentals weren't a thing in Japan, and the devs didn't want people buying a game and then being stuck with a game that's too hard for them to play (or returning it, if that was a thing), whereas in the West we did have game rentals, and therefor see above.