Because that's what lead to the flood of "souls-like" games that intentionally have a bad design, because it encourages toxic competitiveness, encourages mocking and shaming online based on "performance".

A lot of games either don't let you make the game easier, or "punish" you for it (no unlocks, no achievements, no progress, etc) because they try to appeal to the stupid "hardcore gamers". You have a disability, a situation that makes things harder, not enough money to buy the proper kind of controller, or anything else? Well fuck you, you do not deserve to play the game, and if you try you're going to be bullied for it.

If everyone had no problem with the idea that allowing to adjust precisely the difficulty of a game was mandatory, then sure. But until then, the toxic culture of "hardcore" needs to die because it just makes things worse for a lot of people, with no added value.

Also, the initial reason games were hardcore were either bad (or none at all) game design, or as a scam so that you keep on putting money in the machine to continue playing. Then boomers started crying about "new generations" when games became more accessible, and that's when people started thinking that a game being easy means that it's shit. It all comes from a bunch of boomers and edgelords.