Because they made “Cookie Cutter” squads, where you had to have XYZ perks in order to be on the same playing field as others. This is a common issue in video games, if you do not use X or Y gun then you will be at a disadvantage compared to others. Hardline suffered from this on a scale that was so great that it killed the game. In hardline if you did not use the K10 (the vector) you were just out gunned no matter what. IDK what Visceral was thinking adding in a gun that can fire at 1200 rpm with a damage that was equal to the other guns. Most SMGs ran at 24 damage per shot, the K10 ran at 20 damage per shot with a mag size that was only 5 rounds less. But the damage per second was 400 damage per second, meaning you needed only to fire for 0.25 seconds to kill a person vs about 0.4 seconds for a gun that fires 800 rpm. This was the case for most classes, you had 1 to 2 power weapons that greatly outclassed all other weapons. Sadly Visceral ¯_(ツ)_/¯ up hard and didn’t patch the game for well over a month, in fact they put out patch notes announcing the balance changes then waited 30 days before pushing the patch out. Then there was the case of the trunk RPGs, where you had the option to buy an upgrade for the cars where you could pull out an RPG from the truck that would instant kill vehicles…once again if you didn’t have it, you were at a massive disadvantage due to the enemy team using RPGs and killing all vehicles they could see (which some game modes were centered around driving vehicles).
So by DICE removing perks, it removed a Cookie Cutter system from the game.
Could they have worked to balance all perks? Yes and No, the issue is not that some perks were godly, it’s that some were downright useless. Let’s look at BF3 for example, you had
Sprint (longer sprint time and faster sprint)
Flak (reduce damage from explosives)
Explosive (increased the amount of explosives and rockets you could carry)
Cover (reduced suppression effects)
Suppressive (increased suppressive effect of your rounds)
Grenade (increased the amount of hand grenades and 40mm grenades you could carry)
Ammo (increased the amount of primary and secondary ammo you could carry)
Now out of these you would want to use Flak, Cover, Grenade, Explosive.
This is due to the fact that all perks were shared by the squad, which meant that your squad would have less suppression, more grenades and explosives, and take less damage from explosives. This is the optimal setup for a squad, the sprint could be swapped with grenade, but that would be better for Rush. Ammo could be negated by a support (which every squad should have), suppressive would be meh due to the amount of suppression during any firefight.
In BF1, these perks would be too much, no matter how you spin them, they would just be too powerful or would not even provide enough effectiveness to be useful.