Do you actually know what salary sacrifice is?
I'm in HR, and since I work interim and freelance roles, I see a LOT of pension scenes. Very few use salary sacrifice. In fact, I have introduced it in two places.
Most final salary type schemes can't use it, so that takes most of the public sector out of this issue.
I've set up Nest-type schemes three times now, on the auto enrol system, and they don't use it.
Yes, your employer will take your pension from your salary, but that itself is not what salary sacrifice means.
As some posters have said, the employer saves the NI as well as the employee (I suspect more have started to look at it now NI has increased for employers). And some employers gift it back to the employee, into their pension, as once it is set up that way there is no real cost to the employer (there's a bit of admin because you do need some specific contract terms around it, and changes to payments etc are more restricted), or some gift half back and keep half.
If it's only after the first £2k a year, that also takes out a lot of lower earners from the issue.
And salary sacrifice cannot be used for anyone who is on or earns not much over minimum wage. That takes another raft of people put of this.
So, it's another of those things that will impact the employer more, and better paid employees (of which I am sort of one, but my employer scheme is not sal sac, though it was on my list to look into bringing in). The latter I can get behind. I'm starting to feel that employers are getting the brunt of things right now.