Because literally 90%+ of the people who buy it A) don't even know sliders exist, B) don't play offline, and C) aren't analysing the quality of the game, they're just buying it for the 16/17 data and starting over on Ultimate Team. They buy the game like they'd buy a new bulb - it's just a required payment every now and then, and if it switches on, it's doing its job.
You wonder why people aren't protesting "en masse" - there isn't a "masse" that are complaining. There's us. EA don't care about us.
Get this. FIFA 17 officially sold the most copies of any FIFA on launch day (and no doubt during launch week).
That's not because everyone was blown away by the demo (though I'm sure some were). It's just because everyone has to have FIFA. Nobody's mates (outside of this forum) play PES any more, and if you're a bloke with a console and you follow football, you'll buy a football game.
(The fact that it's bundled with consoles helps, too - something a suspected Konami representative
complained to MCV about last year.)
Bearing all of this in mind... We are
incredibly lucky to have sliders, because we aren't EA's target audience any more, and without them, I wouldn't be able to enjoy the game end-of-story.
As it is, I can get something out of the player career mode.
The fact that sliders exist has no impact on the gameplay of the final product. It's just a relatively simple feature, and nothing would change without it.