It IS your salary. If the employer didn't pay it, YOU would have to pay it anyway. If you are a freelancer, you will have to pay that employers share anyway.
It's the cost of social security systems, and someone has to pay it: You. With your work hours and salary.
So if the government reduced the share that the employers pay down to zero tomorrow, would you then go to your partner/family/friends and say "hey, I just got a paycut at work" ?
It doesn't matter how you decide to slice it - "this share you pay, this share I pay" at the end of the day it will be seen through the lens of Total Cost of Ownership.
>>you care only what the end cost is to you.
Yes, so I care what my salary is. What the employer has to legally pay to employ me is literally irrelevant other than academically. It's not my salary, the same how their cost of maintaining an office or providing me with equipment to do my job isn't my salary.