It is because console-simplification of games are making games less and less challenging and thus cheapening the achivements from being true achievements. You cant call breathing an achievement IRL for example. They are supposed to mostly be challenges, but when most people have almost all of them they lose their value imo.
One example of consoles cheapening PC achievement value is cross-platform games.
The ultimate showcase for such is the cover mechanic in gears of war or mass effect 2+
You are basicly (atleast close to) immortality in cover, on harder difficulties you most often simply have less uptime on out-of-cover moves before you die.
The whole cover mechanic is good to the ones who cant see how catered to consoles the controls are. I would call the mechanic artificial difficulty.
Mouse and keyboard allows for perfect mobility, even dark souls I played with zero mobility difficulties despite everyone saying "Dark souls is too hard with mouse and keyboard better get a controller!". Something that shows how noob (for a lack of a better word) gamers has become.
Console gaming has decreased the skillcap for gaming. This to satisfy less-intellectual people with short attention span and no motor skills which crave an instant reward gaming experience to give them the illusion of their achievements being something earned. Achievements has simply become an ego-booster for the insecure with little to no actual challenge.
Try playing divinity original sin or fallout 2 on a console. Consoles also utilize auto-aim in a sad attempt to copy the superior controls of mouse and keyboard.
I really want to specify a last argument I have with a metaphor, but the last time I did that I got banned by an oversensitive moderator who completely missed the point

So I'll leave it there.
I am always open to being wrong, so if you have good arguments for why Im wrong Im willing to listen.