Why is anyone still talking 4-3 or 3-4, when the base personnel package in the league is Nickel against a base offensive 11 personnel?
I see a Big Nickel version of 4-2-5, with an in the box SS rather than a CB. That's our base.
This has become a common refrain.
But it's just misunderstanding the discussion.
There is a 4-2-5 base nickel and a 3-3-5 base nickel.
The down number is still different.
If your SS is a box SS/LB in the 4-2-5 then you are in fact in a 4-3.
It mirrors High school and college.
The scheme isn't so much changing as the players are just smaller and faster to cover more of the field.
Why do players care? Technique and responsibility. Defensive players have very few years to earn a living so seldom want to play out of position or in a way that lowers their value.
A guy who has been drafted and trained to shoot gaps does not want to now 2 gap and read.